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

#define T int 
typedef pair<T, T> pii;
typedef tuple<T, T, T> tii;

#define fr first
#define sc second
#define mp make_pair
#define mt make_tuple
#define pb push_back
#define eb emplace_back

#define lowbit(x)    ((x) & -(x))
#define all(x)       (x).begin(), (x).end()
#define rep(i, x, y) for (int i = (x); i <= (y); ++i)
#define per(i, x, y) for (int i = (x); i >= (y); --i)

inline T rd() {
    T x = 0;
    bool f = 0;
    char c = getchar();
    for (; !isdigit(c); c = getchar()) f |= (c == '-');
    for (; isdigit(c); c = getchar()) x = x * 10 + (c ^ 48);
    return f ? -x : x;
}

vector<int> cnt;

int main() {
	int n, ans = 0; cin >> n;
	string s; cin >> s;
	cnt.pb(0);
	for (auto c : s) cnt.pb(cnt.back() + (c == 'W'));
	for (int i = 0; i < n; ++i)
		ans = max(ans, cnt[i + n] - cnt[i]);
	printf("%d\n", ans);
    return 0;
}