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

#define rep(i, a, b) fo(int i = a; i < (b); ++i)
#define all(x) begin(x), end(x)
#define sz(x) (int)(x).size()
typedef pair<int, int> pii;
typedef vector<int> vi;

int main() {
cin.tie(0)->sync_with_stdio(0);
cin.exceptions(cin.failbit);

ll n;
cin >> n;
string s;
cin >> s;

vector<ll> xsum(n+1, 0), osum(n+1, 0); // xsum[i] .. number of X in <0;i)
for(ll i = 0; i < n; i++) {
    if(s[i] == 'X') {
        xsum[i+1] = xsum[i]+1;
        osum[i+1] = osum[i];
    } else {
        xsum[i+1] = xsum[i];
        osum[i+1] = osum[i]+1;
    }   
}

ll res = 0;
for(ll side = 3; side <= sqrt(n); side++) {
    ll len = side*side;
    ll xreq = 4*side-4;
    ll oreq = (side-2)*(side-2);
    ll cnt = xreq+oreq;
    // assert(cnt == len);
    // cerr << "side " << side << endl; 
    // cerr << "xreq " << xreq << endl;
    // cerr << "oreq " << oreq << endl;
    for(ll i = 0; i <= n-cnt; i++) {
        ll xcnt = xsum[i+cnt]-xsum[i];
        ll ocnt = osum[i+cnt]-osum[i];
        if(xcnt == xreq && ocnt == oreq)
            res++;
        if(xcnt == oreq && ocnt == xreq)
            res++;
    } 
}
cout << res << endl;
}