#include <bits/stdc++.h>
using namespace std;
typedef pair<int, int> pii;

inline int rd() {
	int 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;	
}

#define fr first
#define sc second
#define eb emplace_back
#define rep(i, a, b) for (int i = (a); i <= (b); ++i)

#define N 100

char col[N];

vector<pii> B, G;

int main(){
	int n = rd();
	scanf("%s", col + 1);
	rep(i, 1, n) {
		int x = rd(), y = rd();
		col[i] == 'B' ? B.eb(x, y) : G.eb(x, y);
	}
	int b = B.size(), g = G.size();
	auto sqr = [&](int x) {return x * x;};
	auto dis = [&](pii a, pii b) {
		return sqrt(sqr(a.fr - b.fr) + sqr(a.sc - b.sc));	
	};
	double ans = 0;
	rep(i, 0, b / 2 - 1) ans += dis(B[i], B[i + b / 2]);
	rep(i, 0, g / 2 - 1) ans += dis(G[i], G[i + g / 2]);
	printf("%.10lf\n", ans);
	return 0;
}