#include <bits/stdc++.h>
using namespace std;
const int SIZE = 2e5 + 5;
string S;
int ps[2][SIZE];
int tree[2 * SIZE];
void modify(int pos, int val)
{
for (; pos < 2 * SIZE; pos += (pos & -pos))
tree[pos] += val;
return;
}
int query(int pos)
{
int ret = 0;
for (; pos; pos -= (pos & -pos))
ret += tree[pos];
return ret;
}
long long vv[SIZE];
long long eval(int x, int N)
{
x %= N;
if (vv[x])
return vv[x];
for (int i = 0; i < 2 * N; i++)
{
tree[i] = 0;
}
long long ans = 0;
vector<pair<int, int>> seg;
for (int i = 0; i < N; i++)
{
seg.push_back({ps[0][i], ps[1][(i + x) % N]});
seg.push_back({ps[1][(i + x) % N], ps[0][i]});
}
sort(seg.begin(), seg.end());
for (auto i : seg)
if (i.second > i.first)
ans += query(i.second),
modify(i.second, 1);
else
modify(i.first, -1);
return vv[x] = ans;
}
int main()
{
int N;
S.resize(2 * SIZE);
scanf("%d\n%s", &N, &S[0]);
int ptr[2] = {0, 0};
for (int i = 0; i < 2 * N; i++)
ps[S[i] == 'W'][ptr[S[i] == 'W']++] = i;
long long water_line = eval(0, N);
if (eval(1, N) >= water_line)
{
int L = 0, R = N - 1, M;
while (L != R)
{
M = (L + R + 1) / 2;
if (eval(M, N) < water_line)
R = M - 1;
else
L = M;
}
L = 0;
while (L != R)
{
M = (L + R) / 2;
if (eval(M, N) < eval(M + 1, N))
L = M + 1;
else
R = M;
}
printf("%lld\n", eval(L, N));
}
else
{
int L = 0, R = N - 1, M;
while (L != R)
{
M = (L + R) / 2;
if (eval(M, N) > water_line)
R = M;
else
L = M + 1;
}
R = N;
while (L != R)
{
M = (L + R) / 2;
if (eval(M, N) < eval(M + 1, N))
L = M + 1;
else
R = M;
}
printf("%lld", eval(L, N));
}
return 0;
}
