What's wrong with the test 10?

#include<stdio.h>

int main(){
long unsigned int x,y=0,z=0,q,p,r;

scanf("%lu",&r);

x=r;
q=r*r;

do{
p=q-y*y;
 while( x*x >= p && x >= 0 )x--;
z+=(x+1);
y++;
}while(y<r);

z*=4;
printf("%lu\n",z);

return 0;
}

Используй long long  и/или long double