#include <bits/stdc++.h>
#define ll long long
 
using namespace std;
int main()
{
	ll t;
	cin>>t;
	while(t--)
	{
		ll lec;
		cin>>lec;
		string s;
		cin>>s;
		lec=s.size();
		ll att=0;
		ll req;
		for(ll i=0;i<lec;i++)
		{
			if(s[i]=='P')
			{
				att++;
			}
		}
		if((att*100)/lec<75)
		{
			ll prox=0;
			req=((75*lec)/100-att)+1;
			//cout<<req<<endl;
			for(int i=2;i<=lec-3;i++)
			{
				bool y = s[i-1]=='P'||s[i-2]=='P';
				bool z = s[i+1]=='P'||s[i+2]=='P';
				bool res=y&&z;
				if(res&&prox<req)
				{
					prox++;
				}
 
			}
			if(prox>=req)
			{
				cout<<prox<<endl;
			}
			else
			{
				cout<<"-1"<<endl;
			}
		}
		else 
		{
		cout<<"0"<<endl;
		}
 
	}
}
 
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