#include <iostream>
#include <string>
#include <cctype>
using namespace std;
int main()
{
	string s = "Today was hot and I had a hot tea";
	string xold = "hot";
	string xnew = "cold";
	int strsub( string s, string xold, string xnew );
	cout << strsub( s, xold, xnew ) << endl;
	return ( 0 );
}

string strsub( string s, string xold, string xnew )
{
	string sum = "";
	bool isqualified = 0;
	for( int i = 0; i < s.size(); )
	{
		if( s.substr( i, xold.size() ) == xold )
		{
			if( isqualified == 0 )
			{
				i += xnew.size();
				sum += xnew;
				isqualified = 1;
				cout << sum << endl;
			}
		}
		else
		{
			sum += s[i];
			i += 1;
			cout << sum << endl;
		}
	}
	return( sum );