import java.util.*;

class Solution {

    public static void main(String args[]) {
        Scanner in = new Scanner(System.in);
        int n = in.nextInt();
        int m1 = in.nextInt()*n;
        int m=m1;
        char[] alphabet = "ZYXWVUTSRQPONMLKJIHGFEDCBA".toCharArray();
        String sBefore="0";
        String[] string;
        string=new String[m];
        int count=0;
        int amount=-1;
        int best=1;
        String[] values;
        values=new String[1000];
        String best1="error";
        String s="";
        int v = -10000;
        for (int i = 0; i < n; i++) {
            s = in.next()+s;
        }
        System.err.println(s);
        while(true) {
            m=s.length();
            for (int j=0;j<m-1;j++) {
                string[j]=String.valueOf(s.charAt(j))+""+String.valueOf(s.charAt(j+1));
            }
            for (int j=0;j<m-1;j++) {
                for (int k=0;k<m-1;k++) {
                    if (string[j].equals(string[k])==true &&v!=k-1) {
                        amount++;
                        v=k;
                    }
                }
                if (amount>best) {
                    best=amount;
                    best1=string[j];
                }
                amount=-1;
            }
            String s1=s.replaceAll(best1, String.valueOf(alphabet[count]));
            System.err.println(s);
            values[count]=alphabet[count]+" = "+best1;
            s=s1;
            best1="error";
            best=0;
            count++;
            if (sBefore.equals(s)) {
                break;
            }
            sBefore=s;
        }
        System.out.println(s);
        m=m1;
        for (int h=0;h<count-1;h++) {
            System.out.println(values[h]);
        }
        count=0;
        m=m1;
        sBefore="0";
        string=new String[m];
        count=0;
        amount=-1;
        best=1;
        values=new String[1000];
        best1="error";
    }
}