c++中使用if Conditional的级数总和

#include <iostream>

int main() {
    int n;
    std::cout << "请输入一个正整数n：";
    std::cin >> n;

    int sum = 0;
    for (int i = 1; i <= n; i++) {
        if (i % 2 == 0) {
            sum -= i;
        } else {
            sum += i;
        }
    }

    std::cout << "级数总和为：" << sum << std::endl;

    return 0;
}