#include <bits/stdc++.h>
using namespace std;
int main() {
  int n;
  cin >> n;
  string s;
  cin >> s;
  int a[n];
  for (int i = 0; i < n; i++) cin >> a[i];
  int ans = 1e9;
  for (int i = 0; i < n - 1; i++)
    if (s[i] == 'R' && s[i + 1] == 'L') ans = min(ans, (a[i + 1] - a[i]) / 2);
  if (ans == 1e9)
    cout << -1 << endl;
  else
    cout << ans << endl;
  return 0;
}
