CodeForces - 4C Registration system

https://vjudge.net/problem/CodeForces-4C

#include<iostream>
#include<algorithm>
#include<unordered_map>
using namespace std;
int main()
{
	int n;
	while(cin>>n)
	{
		unordered_map<string,int> q;
		string s;
		for(int i=0;i<n;i++)
		{
			cin>>s;
			if(q.find(s)==q.end())
			{
				q[s]=0;
				cout<<"OK\n";
			}
			else
			{
				cout<<s<<q[s]+1<<"\n";
				q[s]++;
			}
		}
	}
	return 0;
}