编写c++程序。按下面的公式求sum的值。sum=1!+2!+3!+4!+5!

以下是一个C++程序，用于按照给定公式计算sum的值：

#include <iostream>
using namespace std;

int factorial(int n) {
    int fact = 1;
    for (int i = 1; i <= n; i++) {
        fact *= i;
    }
    return fact;
}

int main() {
    int n;
    double sum = 0;
    
    cout << "输入n: ";
    cin >> n;
    
    for (int i = 1; i <= n; i++) {
        sum += factorial(i);
    }
    
    cout << "sum = " << sum << endl;
    
    return 0;
}