a121. 質數又來囉 | From: [114.27.72.98] | 發表日期 : 2012-07-16 22:26

import java.util.Scanner;

public class a121{

public static void main(String [] argv){

Scanner abc = new Scanner(System.in);

while(abc.hasNext()){

int a = abc.nextInt();

int b = abc.nextInt();

int o = 0;

boolean i = true;

int d =(int) Math.sqrt(b);

for(long c = a;c <= b;c++){

if(c == 1)i=false;

if(c == 2)i=true;

if(c == 3)i=true;

if(c == 5)i=true;

if(c == 7)i=true;

if(c != 2 && c % 2==0)i=false;

if(c != 3 && c % 3==0)i=false;

if(c != 5 && c % 5==0)i=false;

if(c != 7 && c % 7==0)i=false;

for(int s = 3;s<=d;s= s+2){

if(c % s==0){

i = false;

break;

}

}if(i){

o++;

}

i = true;

}System.out.println(o);

}

}

}