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

int getNumber() {
	int n;
	do {
		cout << "Enter a non-negative number!\n";
		cin >> n;
	} while (cin && n < 0);
	return n;
}

int main() {
    int n = getNumber();
    long double factorial = 1;
    for (int i = 1; i <= n; ++i)
        factorial *= i;
    // cout.precision(2);
    cout << n << "! = "  << factorial;
    return 0;
}