#include<stdio.h> //计算阶乘的函数factorial int factorial(int num) { int i ,a = 1; for(i = 1;i<=num;i++) { a*=i; } return a; } int main() { int n; //定义变量n double sum = 0.0; scanf("%d",&n); for(int i = 1;i<=n;i++) { sum +=(1.0/factorial(i)); } printf("%.2lf",sum); return 0; }