#include "bits/stdc++.h"
using namespace std;

typedef long long ll;

#define deb(...) logger(#__VA_ARGS__, __VA_ARGS__)
template<typename ...Args>
void logger(string vars, Args&&... values) {
  cout << vars << " = ";
  string delim = "";
  (..., (cout << delim << values, delim = ", "));
  cout << '\n';
}

using ld = long double;

void solve() {
  int n;
  string s;
  cin >> n >> s;
  vector<int> cs(n * 2 + 1);
  int ans = 0;
  for (int i = 0; i < n * 2 - 1; ++i) {
    cs[i] = s[i] == 'W';
    if (i > 0) cs[i] += cs[i - 1];
    if (i >= n - 1) ans = max(ans, cs[i] - (i - n ? cs[i - n] : 0));
  }
  cout << ans << '\n';
}

int main() {
  ios::sync_with_stdio(false);
  cin.tie(nullptr);
  int t = 1;
  // cin >> t;
  while(t--) {
    solve();
  }
}