tgamma function

[strling]

Hello!I'm trying to use the tgamma function to solve this problem : https://www.hackerearth.com/may-easy-challenge-15/algorithm/panda-and-chain-reaction/. But I get it wrong every time. Although the example works, some numbers become negative. Can you help me?

 #include <iostream>
#include <cmath>
using namespace std;

int main()
{
    long long t,n,x,i,l;
    cin>>t;
    for(i=1;i<=t;i++)
   {cin>>n;
    cin>>x;
    x=x%1000003;
    l=tgamma(n+1);
    l=l%100003;
    x=x*l;
    cout<<x%1000003<<"\n";
   }
    return 0;
}