#include <iostream> using namespace std; long long factorial(int n); int main() { int n; cin >> n; cout << factorial(n) << endl; return 0; } long long factorial(int n) { // write your code here...... long long sum = 1; if (n == 0) sum = 1; else { for (int i=1; i<=n; i++){ sum *= i; } } return sum; }