#include <bits/stdc++.h>
template <typename Arg1>
void __f(const char* name, Arg1&& arg1) {
  std::cerr << name << " : " << arg1 << "\n";
}
template <typename Arg1, typename... Args>
void __f(const char* names, Arg1&& arg1, Args&&... args) {
  const char* comma = strchr(names + 1, ',');
  std::cerr.write(names, comma - names) << " : " << arg1 << " | ";
  __f(comma + 1, args...);
}
std::pair<int, int> operator+(std::pair<int, int> a, std::pair<int, int> b) {
  return {a.first + b.first, a.second + b.second};
}
std::pair<long long, long long> operator+(std::pair<long long, long long> a,
                                          std::pair<long long, long long> b) {
  return {a.first + b.first, a.second + b.second};
}
std::ostream& operator<<(std::ostream& out, std::pair<int, int> a) {
  out << a.first << " " << a.second << "\n";
  return out;
}
std::ostream& operator<<(std::ostream& out, std::pair<long long, long long> a) {
  out << a.first << " " << a.second << "\n";
  return out;
}
using namespace std;
int main() {
  std::ios_base::sync_with_stdio(false);
  cin.tie(0);
  cout.tie(0);
  ;
  int n, p;
  cin >> n >> p;
  string s;
  cin >> s;
  int a = 0, x, y;
  for (int i = 0; i < n / 2; i++) {
    if (s[i] != s[n - i - 1])
      a += min(abs(s[i] - s[n - i - 1]), 26 - abs(s[i] - s[n - i - 1]));
  }
  if (a == 0) {
    cout << a;
    return 0;
  }
  for (x = 0; x < n / 2; x++) {
    if (s[x] != s[n - x - 1]) break;
  }
  for (int i = 0; i < n / 2; i++) {
    if (s[i] != s[n - i - 1]) y = i;
  }
  p = min(p - 1, n - p);
  if (abs(p - x) > abs(p - y))
    a += abs(p - y);
  else
    a += abs(p - x);
  for (int i = 0; i < n / 2; i++) {
    if (s[i] != s[n - i - 1]) {
      a += abs(i - x);
      x = i;
    }
  }
  cout << a;
}
