#include <bits/stdc++.h>
using namespace std;
const double PI = acos(0) * 2;
const double EPS = 1e-8;
const long long MOD = 1e9 + 7;
const int MAXN = 1e5 + 5;
const int oo = 1e9 + 10;
const double foo = 1e30;
template <class T>
int getbit(T s, int i) {
  return (s >> i) & 1;
}
template <class T>
T onbit(T s, int i) {
  return s | (T(1) << i);
}
template <class T>
T offbit(T s, int i) {
  return s & (~(T(1) << i));
}
template <class T>
int cntbit(T s) {
  return __builtin_popcounll(s);
}
inline void addmod(int& a, int val, int p = MOD) {
  if ((a = (a + val)) >= p) a -= p;
}
inline void submod(int& a, int val, int p = MOD) {
  if ((a = (a - val)) < 0) a += p;
}
inline int mult(int a, int b, int p = MOD) { return (long long)a * b % p; }
int n;
char s[200100];
int a[200100];
int ans = oo;
int main() {
  cin >> n;
  for (int i = 0; i < n; i++) cin >> s[i];
  for (int i = 0; i < n; i++) cin >> a[i];
  for (int i = 0; i < n - 1; i++) {
    if (s[i] == 'R' && s[i + 1] == 'L') {
      ans = min(ans, a[i + 1] - a[i]);
    }
  }
  if (ans == oo) {
    cout << -1;
    return 0;
  }
  cout << ans / 2;
}
