// by Errichto
#include<bits/stdc++.h>
using namespace std;

const int nax = 1e6 + 5;
char s[nax];

int main() {
    int n, k;
    scanf("%d%d", &n, &k);
    scanf("%s", s);
    for(int i = 0; i < n; ++i) {
        char best_letter = s[i];
        int best_distance = 0;
        for(char maybe = 'a'; maybe <= 'z'; ++maybe) {
            int distance = abs(maybe - s[i]);
            if(distance <= k && distance > best_distance) {
                best_distance = distance;
                best_letter = maybe;
            }
        }
        k -= best_distance;
        s[i] = best_letter;
    }
    if(k > 0) puts("-1");
    else printf("%s\n", s);
    return 0;
}