这么难得题，居然普及-？做了好久

#include <bits/stdc++.h>

using namespace std;

int fact[21];

void solve(int n) {

	if(n == 0) {cout << 0; return;}

	if(n == 2) {cout << 2; return;}

	while(n) {

		int x = floor(log(n)/log(2));

		if(x!=1){cout << 2 << '(';

		solve(x);} else {cout << 2;

		}

		n-=fact[x];

		if(x!=1)cout << ')' ;

		if(n) cout << '+';

	}

}

int main() {

	int ans = 1;

	for(int i = 0; i<=20; i++) {

		fact[i] = ans;

		ans *= 2;

	}

	int n;

	cin >> n;

	solve(n);

	return 0;

}