#include <stdio.h>
int main () {
   double tatole_sum = 0.0 ;
   double single_num = 1.0;
   for(int i = 1 ;i<=20;i++){
       single_num =single_num * i;
       tatole_sum = tatole_sum +single_num;
   }
   printf("1！+2！+3！ ..+20！= %lf",tatole_sum);
}