P124 第40题 求和

#include<stdio.h>long double jc(int n){long double y;if(n==0)return 1;y=n*jc(n-1);return y;}long double fun(int x){long double Sn;if(x==0)return 1;Sn=fun(x-1)+1/jc(x);return Sn;}int main(){int a;scanf("%d",&a);printf("%lf\n",fun(a));return 0;}