#include <stdio.h>

// Recursive function to calculate factorial
int factorial(int n) {
    if (n == 0 || n == 1) {
        return 1; // Base case
    } else {
        return n * factorial(n - 1); // Recursive call
    }
}

int factorial(int n) {
    if (n == 0 || n == 1) {
        return 1; // Base case
    } else {
        return n * factorial(n - 1); // Recursive call
    }
}

int main() {
    int n;
    scanf("%d", &n); // Read input

    // Check for invalid input
    if (n < 0) {
        printf("Invalid Input");
    } else {
        int result = factorial(n);
        printf("%d", result);
    }

    return 0;
}