1!+2!+......+n!

#include<stdio.h>
int main()
{
  int a = 0;
  int n = 1;
  int sum = 0;
  int i = 0;
  scanf("%d", &i);
  for (a = 1; a <= i; a++)
  {
    n = n * a;
    sum = sum + n;
  }
  
  printf("%d", sum);

  return 0;
}