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;
    
    // write your code here......
    if(n%2==0)
    {
        int i=0;
        while(i<=n)
        {
            sum = sum+i;
            i = i+2;
        }
    }
    else{
        int i=1;
        while(i<n)
        {
            sum = sum+i;
            i = i+2;
        }
    }

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