这题忒难了，总算想到二分法水过了！贴代码纪念一下！

#include <iostream>
#include <algorithm>
#include <cstdio>
#include<queue>
#include<vector>
using namespace std;

int bin(int a, int b)
{
	int start = 0, end = 100, middle;
	if(start - a -b == 0)
		return start;
	
	while(1)
	{
		middle = (start + end) / 2;
		if(middle - a - b == 0)
			return middle;
		else if(middle - a - b > 0)
			end = middle;
		else
			start = middle;
	}
	return -1;
}


int main()
{
	int a, b;
	cin >> a >> b;
	cout << bin(a, b) << endl;
	return 0;
}