class Solution {
    solve(s) {
        var result = "";
        var counter = 1;

        var i;
        var j;

        for(i = 0; i < s.length; i++) {
            var prev = s[i];

            for(j = i+1; j < s.length; j++) {
                var curr = s[j];

                if(prev == curr) {
                    counter = counter + 1;
                } else {
                    result = result + "" + counter + "" + prev;
                    counter = 1;
                }

                prev = curr;
                i = j;
            }
        }

        return result + "" + counter + "" + curr;
    }
}