#include <stdio.h>

int main() 
{
    int a = 0;
    scanf("%d",&a);
    int b = 0;
    
    for(int i = 1;i<=a;i++)
    {
        int m = 1;
        for(int j = 1;j<=i;j++)
        {
             m = j*m;
        }
        b = b+m;
    }
    printf("%d",b);
    return 0;
}