Q.使用long long int 應該夠用了吧...錯在哪裡了呢？能否給個方向？謝謝～

#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <stdbool.h>
#include <math.h>

long long int gcd(long long int, long long int);

int main(int argc,char* argv[]) {

    long long int a = 0,b = 0,x = 0,y = 0,gcd_of_x_and_y = 0,lcm_of_x_and_y = 0,ans = 0;
    while(scanf("%I64d %I64d %I64d %I64d",&a,&b,&x,&y)==4) {

        //須考慮x,y是否為0的各種情況
        //另須特別考慮x為y的倍數或y為x的倍數之特別情況
        if(x==0&&y!=0) {
            //a<=0<=b
            if(a*b<=0) {
                //[a,b]範圍中包含0
                ans = abs(floor(abs(a)/abs(y))+floor(abs(b)/abs(y)))+1;
                //a*b>0
            } else if(a*b>0 ) {

                ans = abs(floor(abs(a)/abs(y))-floor(abs(b)/abs(y)));
                //printf("ans = %I64d\n",ans);

                //a<b<0
                if((a<0)&&(b<0)) {
                    if(abs(b)%abs(y)==0) {
                        ans+=1;
                        //printf("ans = %I64d\n",ans);
                        //system("PAUSE");
                    }

                    //(a>0)&&(b>0)
                } else {

                    if(abs(a)%abs(y)==0)
                        ans+=1;
                }
            }
        } else if(x!=0&&y==0) {
            //a<=0<=b
            if(a*b<=0) {
                //[a,b]範圍中包含0
                ans = abs(floor(abs(a)/abs(x))+floor(abs(b)/abs(x)))+1;
                //a*b>0
            } else  if(a*b>0) {
                ans = abs(floor(abs(a)/abs(x))-floor(abs(b)/abs(x)));

                if((a<0)&&(b<0)) {
                    if(abs(b)%abs(x)==0)
                        ans+=1;

                    //(a>0)&&(b>0)
                } else {

                    if(abs(a)%abs(x)==0)
                        ans+=1;
                }
            }

        } else if(x==0&&y==0) {
            if(a*b<=0) {
         //[a,b]範圍中包含0
                ans = 1;
                //a*b>0
            } else if(a*b>0 ) {
        ans = 0;
            }

            //x!=0 && y!=0
        } else {
            //a<=0<=b
            if(a*b<=0) {
                if(x%y==0) {
                    ans = abs(floor(abs(a)/abs(y))+floor(abs(b)/abs(y)))+1;
                } else if(y%x==0) {
                    ans = abs(floor(abs(a)/abs(x))+floor(abs(b)/abs(x)))+1;

                    //(x%y! =0)&&(y%x!=0)
                } else {
                    //為方便起見 gcd_of_x_and_y及lcm_of_x_and_y全定義為正數

                    gcd_of_x_and_y = gcd(abs(x),abs(y));
                    lcm_of_x_and_y = abs(x*y)/gcd_of_x_and_y;

                   // printf("gcd_of_x_and_y = %I64d\n",gcd_of_x_and_y);
                    //printf("lcm_of_x_and_y = %I64d\n",lcm_of_x_and_y);
                   // system("PAUSE");

                    ans = (floor(abs(a)/abs(x))+floor(abs(b)/abs(x)))+(floor(abs(a)/abs(y))+floor(abs(b)/abs(y)))-(floor(abs(a)/abs(lcm_of_x_and_y))+floor(abs(b)/abs(lcm_of_x_and_y)))+1;

                    if(abs(a)%abs(x)==0)
                        ans+=1;
                    if(abs(a)%abs(y)==0)
                        ans+=1;
                    if(abs(a)%abs(lcm_of_x_and_y)==0)
                        ans-=1;
                }
                //a*b==0
            }
            //a*b>0
            else if(a*b>0) {

                //為方便起見 gcd_of_x_and_y及lcm_of_x_and_y全定義為正數
                gcd_of_x_and_y = gcd(abs(x),abs(y));
                lcm_of_x_and_y = abs(x*y)/gcd_of_x_and_y;

                //printf("gcd_of_x_and_y = %I64d\n",gcd_of_x_and_y);
                //printf("lcm_of_x_and_y = %I64d\n",lcm_of_x_and_y);

                if((a<0)&&(b<0)) {

                    if(x%y==0) {
                        ans = abs(floor(abs(a)/abs(y))-floor(abs(b)/abs(y)));
                        if(abs(b)%abs(y)==0)
                            ans+=1;

                    } else if(y%x==0) {
                        ans = abs(floor(abs(a)/abs(x))-floor(abs(b)/abs(x)));
                        if(abs(b)%abs(x)==0)
                            ans+=1;

                        //(x%y!=0)&&(y%x!=0)
                    } else {
                        ans = (floor(abs(a)/abs(x))-floor(abs(b)/abs(x)))+(floor(abs(a)/abs(y))-floor(abs(b)/abs(y)))-(floor(abs(a)/abs(lcm_of_x_and_y))-floor(abs(b)/abs(lcm_of_x_and_y)))+1;
                        // printf("ans = %I64d\n",ans);

                        if(abs(b)%abs(x)==0)
                            ans+=1;
                        //printf("ans = %I64d\n",ans);
                        if(abs(b)%abs(y)==0)
                            ans+=1;
                        //printf("ans = %I64d\n",ans);
                        if(abs(b)%abs(lcm_of_x_and_y)==0)
                            ans-=1;
                        //printf("ans = %I64d\n",ans);
                    }
                    //a>0 && b>0
                } else if((a>0)&&(b>0)) {

                    if(x%y==0) {
                        ans = abs(floor(abs(a)/abs(y))-floor(abs(b)/abs(y)));
                        if(abs(b)%abs(y)==0) {
                            ans+=1;
                        }
                    } else if(y%x==0) {
                        ans = abs(floor(abs(a)/abs(x))-floor(abs(b)/abs(x)));
                        if(abs(b)%abs(x)==0) {
                            ans+=1;
                        }
                        //(x%y!=0)&&(y%x!=0)
                    } else {
                        ans = (floor(abs(b)/abs(x))-floor(abs(a)/abs(x)))+(floor(abs(b)/abs(y))-floor(abs(a)/abs(y)))-(floor(abs(b)/abs(lcm_of_x_and_y))-floor(abs(a)/abs(lcm_of_x_and_y)))+1;

                        if(abs(a)%abs(x)==0)
                            ans+=1;
                        if(abs(a)%abs(y)==0)
                            ans+=1;
                        if(abs(a)%abs(lcm_of_x_and_y)==0)
                            ans-=1;
                    }
                }
            }
        }

        printf("%I64d\n",ans);
    }

    return 0;
}


long long int gcd(long long int p,long long int q) {
    if(p%q==0) {
        return q;
    } else {
        return gcd(q,p%q);
    }
}