i dont know why i ahve got WA7

Here is my code(pls help me :D)

#include<stdio.h>
#include<math.h>

long i, j, r;
unsigned long nr;

int main()
{
    scanf("%ld", &r);

    for(i = 1; i <= r; i++)
        for(j = 1; j <= r; j++)
            if((double)(sqrt(i * i + j * j) - r) >= sqrt(2))
                nr++;

    nr = r * r * 4 - nr * 4;

    printf("%ld\n", nr);

    return 0;
}

Edited by author 25.09.2008 14:42