#include <iostream>
#include <map>
#include <string>
using namespace std;
int main()
{
	int n;
	cin>>n;
	while(n--)
	{
		map<char, int> count;
		map<char, int>::iterator iter;
		
		int m;
		string temp;
		cin>>m>>temp;
		for(int i=0; i<temp.length(); i++)
		{
			iter=count.find(temp[i]);
			if(iter==count.end() )
			{
				count[temp[i]]=1;
			}
			else
			{
				count[temp[i]]=iter->second+1;
			}
		}
	}
	return 0;
}

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