getting SIGSEGV for MARBLES question

i am not sure why i am getting this error.please help.my code is given below.

#include<stdio.h>
double find_ncr(unsigned long long n,unsigned long long  r)
{
   if(n<r)
    return 0;
   else if(n==r)
    return 1;
   else if(r==1)
    return n;
   if(n==1)
    return 1;
   return find_ncr(n-1,r)+find_ncr(n-1,r-1);
}

int main()
{
   unsigned long long n, r;
   unsigned long long t;
   scanf("%llu",&t);
   while(t--)
   {
       scanf("%llu%llu",&n,&r);
       if(r<=n/2)
        printf("%.0lf\n",find_ncr(n-1,r-1));
       else
       printf("%.0lf\n",find_ncr(n-1,n-r));
   }
   return 0;
}