题解 | #求 1 - n 之间偶数的和#

#include <iostream>
using namespace std;

int main() {
    
    int n;
    cin >> n;
    int sum = 0;
    
    int i;
    for(i = 1 ; i <= n ;i++)
        if(i % 2 == 0)
        sum += i;
    

    cout << sum << endl;
    
    return 0;
}