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

const int N = 1000;

int a[N], b[N];
int al, bl;

void add(int a[], int &al, int b[], int &bl) {
    int t = 0;
    al = max(al, bl);
    for (int i = 0; i < al; i++) {
        t += a[i] + b[i];
        a[i] = t % 10;
        t /= 10;
    }
    if (t) a[al++] = 1;
    while (al > 1 && a[al-1] == 0) al--;
}

void mul(int a[], int &al, int b[], int &bl) {
    int t = 0;
    int c[N] = {0};
    for (int i = 0; i < al; i++)
        for (int j = 0; j < bl; j++)
            c[i + j] += a[i] * b[j];
    al += bl;
    for (int i = 0; i < al; i++) {
        t += c[i];
        a[i] = t % 10;
        t /= 10;
    }
    while (al > 1 && a[al-1] == 0) al--;
}

int main() {
    int n;
    cin >> n;
    
    int sum[N] = {0}, sum_len = 1;
    int fact[N] = {1}, fact_len = 1;
    
    for (int i = 1; i <= n; i++) {
        // 计算当前阶乘 i! = (i-1)! * i
        int num = i;
        int temp[N] = {0}, temp_len = 0;
        while (num) {
            temp[temp_len++] = num % 10;
            num /= 10;
        }
        mul(fact, fact_len, temp, temp_len);
        
        // 将阶乘结果加到总和中
        add(sum, sum_len, fact, fact_len);
    }
    
    for (int i = sum_len - 1; i >= 0; i--) {
        cout << sum[i];
    }
    cout << endl;
    
    return 0;
}