#include <stdio.h>
#include <math.h>
int N,Mycase=0;
int main()
{
    while (EOF!=scanf("%d",&N))
    {
        if (N<=0)
            break;
        printf("Case %d: %.0f\n",++Mycase,ceil(log(N)/log(2.0)));
    }
    return 0;
}

 Why does this code get WA?

 I dont have any idea .

Please help me .  thank you ^^~