Problem using tgamma() function

[abdalimran]

tgamma() function shows different result for same logic. Code are given below..

#include <iostream>
#include <cstdio>
#include <cmath>

using namespace std;

int main()
{
    int n;

    while(cin>>n)
    {
        int fact = tgamma(n+1);
        cout<<fact<<endl;
    }

    return 0;

Input: 6
Output: 719


But when i write as following:

#include <iostream>
#include <cstdio>
#include <cmath>

using namespace std;

int main()
{
    int n;

    while(cin>>n)
    {
        cout<<tgamma(n+1)<<endl;
    }

    return 0;

Input: 6
Output: 720

Why the difference? What happens here?

[mik2718]

tgamma returns a double

so the first one casts it to an int, the second one doesn't