#include <bits/stdc++.h>
using namespace std;
const int LEN = 50 * 2 + 50;
int n;
int aLen, sLen;
int a[LEN + 5], s[LEN + 5];
int main()
{
    cin >> n;

    // 构建高精度的 0! 以及高精度的 0
    aLen = 1;
    a[0] = 1;
    sLen = 1;
    s[0] = 0;

    // n 次，每次算出 i!，然后累加进 s
    for (int i = 1; i <= n; i++)
    {
        // 【计算 i!】
        for (int j = 0; j < aLen; j++)
            a[j] *= i;
        for (int j = 0; j < aLen - 1; j++)
        {
            a[j + 1] += a[j] / 10;
            a[j] %= 10;
        }
        while (a[aLen - 1] > 9)
        {
            a[aLen] = a[aLen - 1] / 10;
            a[aLen - 1] %= 10;
            aLen++;
        }
        // 【s += i!】
        sLen = max(sLen, aLen);
        for (int i = 0; i < sLen; i++)
            s[i] += a[i];
        for (int j = 0; j < sLen - 1; j++)
        {
            s[j + 1] += s[j] / 10;
            s[j] %= 10;
        }
        while (s[aLen - 1] > 9)
        {
            s[sLen] = a[sLen - 1] / 10;
            s[sLen - 1] %= 10;
            sLen++;
        }
    }

    // 输出
    for (int i = sLen - 1; i >= 0; i--)
        cout << s[i];
    return 0;
}