#include <bits/stdc++.h>
using namespace std;
char g[100001];
int n, p;
int res;
int main() {
  scanf("%d%d", &n, &p);
  res = 0;
  scanf("%s", g);
  --p;
  if (p * 2 >= n) p = n - 1 - p;
  int mn = -1, mx = -1;
  int sum = 0;
  for (int i = 0; i < n / 2; ++i) {
    sum += min(abs(g[i] - g[n - i - 1]), 26 - abs(g[i] - g[n - i - 1]));
    if (g[i] != g[n - i - 1]) {
      if (mn == -1) mn = i;
      mx = i;
    }
  }
  if (mn == -1) mn = mx = p;
  if (sum) res = min(abs(p - mn) + abs(mn - mx), abs(p - mx) + abs(mx - mn));
  printf("%d\n", sum + res);
}
