#include <bits/stdc++.h>
#pragma GCC optimize("O3")
#pragma GCC optimize("Ofast")
#pragma GCC optimize("unroll-loops")
#pragma GCC target("avx,avx2,fma")
using namespace std;
typedef long long ll;
typedef pair<ll, ll> pll;
typedef pair<int, int> pii;
#define MAX 303030
#define MAXS 70
#define INF 1'000'000'100'000'000'000
#define bb ' '
#define ln '\n'
#define Ln '\n'
#define MOD 1'000'000'007
#define TC 1
typedef long double ld;
ll sq(ll x) { return x * x; }
ld getdis(pii p1, pii p2) {
	return sqrt(sq(p1.first - p2.first) + sq(p1.second - p2.second));
}
signed main() {
	ios::sync_with_stdio(false), cin.tie(0);
	int N;
	cin >> N;
	string s;
	cin >> s;
	int i;
	vector<pii> arr[2];
	int a, b;
	for (i = 1; i <= N; i++) {
		cin >> a >> b;
		arr[s[i - 1] == 'B'].push_back(pii(a, b));
	}
	long double sum = 0;
	for (auto c : { 0, 1 }) {
		int n = arr[c].size();
		n >>= 1;
		for (i = 0; i < n; i++) sum += getdis(arr[c][i], arr[c][i + n]);
	}
	cout << fixed;
	cout.precision(20);
	cout << sum;
}