#include <bits/stdc++.h>
using namespace std;
char c[100100 + 1];
int abs(int a) { return a > 0 ? a : -a; }
int dist(int a, int b) { return min(abs(a - b), abs(26 - abs(a - b))); }
int main() {
  int n, p;
  scanf("%d %d\n", &n, &p);
  for (int i = 1; i <= n; i++) scanf("%c", &c[i]);
  if (p > n / 2) p = n - p + 1;
  int k = n / 2, mn = p, mx = p, count = 0;
  for (int i = 1; i <= k; i++)
    if (c[n - i + 1] != c[i]) {
      count += dist(c[i], c[n - i + 1]);
      if (i > p) mx = i;
      if (mn == p && i < p) mn = i;
    }
  int ans1 = mx - p + 2 * (p - mn), ans2 = p - mn + 2 * (mx - p);
  if (mn == p) ans2 = mx - p;
  if (mx == p) ans1 = p - mn;
  cout << min(ans1, ans2) + count << endl;
  return 0;
}
