使用c++，输入整数n, 编程计算 sum=1!+2!+...+n!。

#include <iostream>
using namespace std;

int main() {
    int n;
    double p = 1, sum = 0;
    cout << "请输入一个整数：";
    cin >> n;
    for (int i = 1; i <= n; i++) {
        p *= i;
        sum += p;
    }
    cout << "1!+2!+...+" << n << "! = " << sum << endl;
    return 0;
}