题解

稍微推理一下递归即可

#include <iostream>
#include <cstdio>
#define int long long
using namespace std;
int f(int n){
    if(n == 1) return 1;
    if(n & 1) return f(n >> 1) * 2 + n + (n / 2) * (n / 2);
    return f(n >> 1) * 2 + (n * n) / 4; 
}
signed main() {
	int n;
    cin >> n;
    cout << f(n);
	return 0;
}