#include <iostream>
	#include <string>
	#include <vector>
	#include <algorithm>
	#include <unordered_map>
 
 
	using namespace std;
 
		int main(){
 
			unordered_map<int,int> numbers;
			bool flag = false;
 
			while(cin){
				auto buffer = 1;
				cin >> buffer;
				numbers.insert({buffer,buffer});
			}
 
			for(auto it : numbers){
				int zeroSum = 0 - it.second;
				auto t = numbers.find(zeroSum);
				if(t != numbers.end()){
					cout << it.first << " and " << t->second << " add up to zero " << endl;
					flag = true;
				}
			}
 
			cout << "Function returned " << flag << endl;
		}

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