#include <bits/stdc++.h>

using namespace std;

using pii = pair<int, int>;

int main() {
  int n;
  scanf("%d", &n);
  static char s[55];
  scanf("%s", s);
  vector<int> B;
  vector<int> G;
  for (int i = 0; i < n; ++i) {
    if (s[i] == 'B') {
      B.emplace_back(i);
    } else {
      G.emplace_back(i);
    }
  }
  int b = B.size() / 2, g = G.size() / 2;
  vector<pii> vt(n);
  auto f = [&](int i, int j) {
    double dx = vt[i].first - vt[j].first, dy = vt[i].second - vt[j].second;
    return sqrt(dx * dx + dy * dy);
  };
  for (int i = 0; i < n; ++i) {
    scanf("%d %d", &vt[i].first, &vt[i].second);
  }
  double res = 0;
  for (int i = 0; i < b; ++i) {
    res += f(B[i], B[i+b]);
  }
  for (int i = 0; i < g; ++i) {
    res += f(G[i], G[i+g]);
  }
  printf("%.10lf\n", res);
  return 0;
}