#include<bits/stdc++.h>
#define sq(x) ((x)*(x))
using namespace std;
using ll=long long;
using pll=pair<ll,ll>;
int main(){
    ios::sync_with_stdio(0);
    cin.tie(0);
    ll n;
    string s;
    cin>>n>>s;
    vector<ll>X(n),Y(n);
    for(ll i=0;i<n;i++){
        cin>>X[i]>>Y[i];
    }
    vector<ll>B,G;
    for(ll i=0;i<n;i++){
        if(s[i]=='B'){
            B.push_back(i);
        }else{
            G.push_back(i);
        }
    }
    ll b=B.size()/2,g=G.size()/2;
    double r=0;
    for(ll i=0;i<b;i++){
        ll t=sq(X[B[i]]-X[B[i+b]])+sq(Y[B[i]]-Y[B[i+b]]);
        r+=sqrt(t);
    }
    for(ll i=0;i<g;i++){
        ll t=sq(X[G[i]]-X[G[i+g]])+sq(Y[G[i]]-Y[G[i+g]]);
        r+=sqrt(t);
    }
    cout<<fixed<<r;
}