Calculate the greatest distance between two any same characters in a string. Examples: (in: abba | out: 2), (in: abab | out: 1), (in: aaaabababbbbba | out: 5)

Char Distance Problem

int GetDistance(string val) {
    int max = -1;
    for(var i = 0; i <= val.Length / 2; i++) {
        for(var y = val.Length - 1; y > 0; y--) {
            var dist = (y - i) - 1;
            if(val[i] == val[y] && dist > max) {
                max = dist;
                break;
            }
        }
    }
    return max;
}