#include <bits/stdc++.h>
using namespace std;
int n, p, r2, r1;
char a[100007];
int main() {
  cin >> n >> p;
  for (int i = 1; i <= n; ++i) cin >> a[i];
  for (int i = 1; i <= n / 2; ++i) {
    char c1 = a[i], c2 = a[n - i + 1];
    if (c1 < c2) swap(c1, c2);
    r1 += min(c1 - c2, c2 + 26 - c1);
  }
  if (p <= n / 2) {
    int l = 0, r = 0;
    for (int i = p - 1; i > 0; --i)
      if (a[i] != a[n - i + 1]) l = i;
    for (int i = p + 1; i <= n / 2; ++i)
      if (a[i] != a[n - i + 1]) r = i;
    if (l == 0 && r != 0) r2 = r - p;
    if (l != 0 && r == 0) r2 = p - l;
    if (l != 0 && r != 0)
      r2 = min(r - l + min(p - l, r - p), min(n - l + 1 - p, p + r - 1));
  } else {
    int l = 0, r = 0;
    for (int i = p - 1; i > n / 2; --i)
      if (a[i] != a[n - i + 1]) l = i;
    for (int i = p + 1; i <= n; ++i)
      if (a[i] != a[n - i + 1]) r = i;
    if (l == 0 && r != 0) r2 = r - p;
    if (l != 0 && r == 0) r2 = p - l;
    if (l != 0 && r != 0)
      r2 =
          min(r - l + min(p - l, r - p), min(p - n + r - 1, n - p + n - l + 2));
  }
  cout << r1 + r2;
  return 0;
}
