#include <iostream>
#include <vector>
#include <string>
#include <functional>
#include <cassert>
using namespace std;
typedef long long ll;
const int N = 400000 + 7;
int n;
string s;
int main() {
ios::sync_with_stdio(0); cin.tie(0);
cin >> n >> s;
vector<int> a, b;
for (int i = 0; i < 2 * n; i++) {
if (s[i] != s[0]) {
a.push_back(i);
}
else {
b.push_back(i);
}
}
vector<ll> cnt(n);
ll sol = 0;
for (int shift = 0; shift < n; shift++) {
for (int i = 0; i < n; i++) {
int i2 = (i + shift) % n, l = min(a[i], b[i2]), r = max(a[i], b[i2]);
for (int j = 0; j < n; j++) {
int j2 = (j + shift) % n;
if (l < min(a[j], b[j2]) && min(a[j], b[j2]) < r && r < max(a[j], b[j2])) {
cnt[shift]++;
}
}
}
}
for (auto& x : cnt) {
sol = max(sol, x);
}
cout << sol << "\n";
}
