#include<bits/stdc++.h>
using namespace std;
using ll = long long;

#define fo(a,b) for(int a=0;a<(b);a++)

const int START = 123456;

int n;
char in[1123456];

int main()
{
	ll out = 0;
	scanf("%d %s", &n, in);
	fo(i,n)
	{
		ll ins=0;
		ll outs=0;
		for(int j=i;j<n;j++)
		{
			if(in[j]=='X') outs++;
			else ins++;
			//printf(" > %lld %lld\n", ins, outs);
			if(ins > 0 && outs%4==0 && outs>=8)
			{
				ll Y = (outs-4)/4;
				if(Y*Y==ins)
					out++;
			}
		}

	}
	printf("%lld\n", out);
	return 0;
}