main( )
{
int  a,b=1;
for(a=1;a<=10;a++)
b*=a
printf("%d",b);
}
这总应该对了吧

#include <iostream>
using namespace std;
int factorial (long val)
{
    if (val > 1)
        return factorial(val-1) * val;
    return 1;
}

int main()
{
    long i;
    cin >> i;
    cout << factorial(i) << endl;
    system("pause");
    return 0;
}