UVA 10784 - Diagonal

#include<stdio.h>
#include<math.h>
int main()
{
long n,cas=1,x;
while(scanf("%ld",&n)==1)
{
    if(n==0)
        break;
    x=ceil((3+sqrt(9+8*n))/2);
    printf("Case %ld: %ld\n",cas,x);
    cas++;
}
}