Problem with connection

Connection.cpp

#include <iostream>

using namespace std;

string marge(string a, string b)
{
	string c;
	if(a.length() <= b.length())
	{
		for(int i = 0, j = 0; i < a.length(); i++, j++)
		{
			c += a[i];  
			c += b[i];
		}
	}
	else
	{
		for(int i = 0, j = 0; i < b.length(); i++, j++)
		{
			c += a[i];  
			c += b[i];
		}
	}
	return c;
}

int main()
{
	int n;
	string a, b;
	cin>>n;
	while(n--)
	{
		cin>>a>>b;
		cout<<marge(a,b)<<endl;
	}
}