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

vector<int> mul(vector<int>& a, int b) {
    vector<int> c;
    int t = 0;
    for (int i = 0; i < a.size() || t; i++) {
        if (i < a.size()) t += a[i] * b;
        c.push_back(t % 10);
        t /= 10;
    }
    return c;
}

vector<int> add(vector<int>& a, vector<int>& b) {
    vector<int> c;
    int t = 0;
    for (int i = 0; i < a.size() || i < b.size() || t; i++) {
        if (i < a.size()) t += a[i];
        if (i < b.size()) t += b[i];
        c.push_back(t % 10);
        t /= 10;
    }
    return c;
}

int main() {
    int n;
    cin >> n;
    vector<int> s = {0};
    vector<int> f = {1};
    
    for (int i = 1; i <= n; i++) {
        f = mul(f, i);
        s = add(s, f);
    }
    
    for (int i = s.size() - 1; i >= 0; i--) {
        cout << s[i];
    }
    cout << endl;
    
    return 0;
}