class Result {

    /*
     * Complete the 'alternate' function below.
     *
     * The function is expected to return an INTEGER.
     * The function accepts STRING s as parameter.
     */

    public static int alternate(String s) {
    // Write your code here
    int[][] countMap = new int[26][26];
    char[][] lastChar = new char[26][26];
    
    int ans = 0;
    
    for (int i = 0; i < s.length(); i++){
        char c = s.charAt(i);
        int index = c - 'a' ;
        for (int j = 0; j < 26; j++){
            if (countMap[index][j] == -1 ){continue;}
            if (lastChar[index][j] == c){
                countMap[index][j] = -1;
                countMap[j][index] = -1;
            }
            else{
                lastChar[index][j] = c;
                lastChar[j][index] = c;
                countMap[index][j] += 1;
                countMap[j][index] += 1;
            }    
        }
    }
    for (int i=0 ; i<26 ; i++){
        for (int j=0 ; j < 26 ; j++) {
            if (i==j){continue;}
            ans = Math.max(countMap[i][j], ans);
        }
    }
    if (s.length() == 1){return 0;}

    return ans;
    
    
    }
}