#include <bits/stdc++.h>
using namespace std;
int main() {
  int n = 0, p = 0, ans = 0, mn = 100001, mx = -1, temp = 0;
  cin >> n >> p;
  string s = "";
  cin >> s;
  for (int i = 0; i < n / 2; i++) {
    if (abs(s[i] - s[n - 1 - i]) > 0 && i < mn) mn = i;
    if (abs(s[i] - s[n - 1 - i]) > 0 && i > mx) mx = i;
    ans += abs(s[i] - s[n - 1 - i]) > 13 ? 26 - abs(s[i] - s[n - 1 - i])
                                         : abs(s[i] - s[n - 1 - i]);
  }
  if (mx == -1 && mn == 100001)
    mx = mn = p;
  else
    mx++, mn++;
  ans += mx - mn;
  if (n % 2 != 0) {
    if (p > n / 2) {
      if (p == n / 2 + 1)
        ans += min(abs(p - mx), mn + 1);
      else {
        if (mx != p && mn != p) {
          temp = mn;
          mn = n - mx + 1, mx = n - temp + 1;
          ans += min(abs(mx - p), abs(p - mn));
        }
      }
    } else
      ans += min(abs(mx - p), abs(p - mn));
  } else {
    if (p > n / 2) {
      if (mx != p && mn != p) {
        temp = mn;
        mn = n - mx + 1, mx = n - temp + 1;
        ans += min(abs(mx - p), abs(p - mn));
      }
    } else
      ans += min(abs(mx - p), abs(p - mn));
  }
  cout << ans << endl;
}
