#include <bits/stdc++.h>
using namespace std;
int abs(int a, int b) {
  if (a > b)
    return a - b;
  else
    return b - a;
}
int main() {
  int n, c, i, b, count = 0, index1 = 1, index2 = 1, flag = 0;
  cin >> n >> c;
  char *s;
  s = new char[n + 2];
  for (i = 1; i <= n; i++) {
    cin >> s[i];
  }
  int *d = new int[n + 1];
  for (i = 1; i <= n / 2; i++) {
    b = abs((int)s[i], (int)s[n - i + 1]);
    if (b < 13)
      d[i] = d[n - i + 1] = b;
    else
      d[i] = d[n - i + 1] = 26 - b;
  }
  if (c > n / 2) c = 1 + n - c;
  for (i = 1; i <= n / 2; i++) {
    if (d[i] > 0) {
      index1 = i;
      break;
    }
  }
  for (i = n / 2; i >= 1; i--) {
    if (d[i] > 0) {
      index2 = i;
      flag = 1;
      break;
    }
  }
  if (c <= index1) {
    count = index2 - c;
  } else if (c <= index2) {
    if (c - index1 > index2 - c)
      count = 2 * (index2 - c) + c - index1;
    else
      count = 2 * (c - index1) + index2 - c;
  } else
    count = c - index1;
  for (i = index1; i <= index2; i++) {
    count += d[i];
  }
  if (flag == 1)
    cout << count;
  else
    cout << 0;
  return 0;
}
