#include <bits/stdc++.h>
using namespace std;
int main() {
  int length, req_length;
  char input[1000001];
  scanf("%d %d", &length, &req_length);
  scanf("%s", input);
  if (req_length <= (length * 25)) {
    char outputString[1000001];
    int i = 0;
    int j = 0;
    while (j < length) {
      if (req_length == 0) {
        outputString[i] = input[j];
      } else {
        int input_ascii = (int)input[i];
        int a_ascii = (int)'a';
        int z_ascii = (int)'z';
        int input_m_a = (abs(input_ascii - a_ascii));
        int input_m_z = abs(input_ascii - z_ascii);
        if (input_m_a > input_m_z && input_m_a <= req_length) {
          outputString[i] = 'a';
          req_length = req_length - input_m_a;
        } else if (input_m_z > input_m_a && input_m_z <= req_length) {
          outputString[i] = 'z';
          req_length = req_length - input_m_z;
        } else {
          char k = input[i];
          if (input_m_a > input_m_z) {
            int put = 0;
            while (((char)k) != 'a') {
              if (abs(input[i] - k) == req_length) {
                outputString[j] = k;
                req_length = req_length - abs(input[i] - k);
                break;
              }
              if (((char)k) == 'a') {
                put = 1;
                break;
              }
              --k;
            }
            if (put == 1) {
              outputString[j] = 'a';
              req_length = req_length - abs(input[i] - 'a');
            }
          } else if (input_m_z > input_m_a) {
            int put = 0;
            while (((char)k) != 'z') {
              if (abs(input[i] - k) == req_length) {
                outputString[j] = k;
                req_length = req_length - abs(input[i] - k);
                break;
              }
              if (((char)k) == 'z') {
                put = 1;
                break;
              }
              ++k;
            }
            if (put == 1) {
              outputString[j] = 'z';
              req_length = req_length - abs(input[i] - 'z');
            }
          }
        }
      }
      ++i;
      ++j;
    }
    outputString[i] = '\0';
    if (req_length == 0) {
      printf("%s\n", outputString);
    } else {
      printf("-1\n");
    }
  } else {
    printf("-1\n");
  }
  return 0;
}
