题解 | #求 1 - n 之间偶数的和#

using namespace std;

int main() {
    
    int n;
    cin >> n;
    int sum = 0;
    
    // write your code here......
    for(int i=0;i<=n;i++){
        if(i%2==0){
            sum=sum+i;
        }
    }

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