code/old_homework/12.7_2.cpp

//计算阶乘
#include <iostream>
using namespace std;

/*
int main() {
    int n;
    cin >> n;  // 输入一个正整数n
    long long result = 1;  // 使用long long类型来避免结果溢出
    
    // 计算阶乘
    for (int i = 1; i <= n; ++i) {
        result *= i;
    }

    cout << result << endl;  // 输出阶乘的结果
    return 0;
}
*/

int main(){
    long long sum = 1;
    int n;
    cin >>n;
    int i = 1;
    while (i <= n)
    {
        sum *= i;
        i++;
    }
    cout <<sum<<endl;
    return 0;    
}