How to add array elements to stringstream?

[xeonn eighttwosize]

This is my code:

#include <iostream>
#include <string>
#include <istream>
#include <sstream>
using namespace std;
int main()
{
	string groups[3] = {};
	int groupSize[3] = {}, total = 0;
	stringstream output;

	for (int a=0; a<3; a++)
	{
		cout << "Give group name :";
			cin >> groups[a];
		cout << "Give population size :";
		while(!(cin >> groupSize[a]))
		{
			cout << "Invalid input. Only integers allowed. " << endl;
			cin.clear();
			cin.ignore(numeric_limits<streamsize>::max(), '\n');
		}
		output << groups[a] << ' ' << groupSize[a] << '\n';
	}
	cout << output;
	cin.sync();
	cin.get();

  return 0;
}

It outputs jibberish. I can do what I need to do but I would need to declare more variables and write more cout's, isn't there a way to add these elements to a stringstream or streambuffer? My goal is to write this program and make it as comprehensive as possible but also with very few lines.

[JLBorges]

#include <limits>

line 10:

	// stringstream output;
	ostringstream output ;

line 25:

        // cout << output;
        cout << output.str() ;

line 26:
// cin.sync(); // avoid