import java.util.HashMap;
import java.util.Map;

public class Solution {
    public int hexToDec (String input) {
        //considering valid string input
        if (input == null || input.equals("")) {
            throw new IllegalArgumentException("input is not valid");
        }

        int result = 0;
        int size = input.length();
        Map<Character, Integer> map = new HashMap<Character, Integer>();
        map.put('a', 10);
        map.put('b', 11);
        map.put('c', 12);
        map.put('d', 13);
        map.put('e', 14);
        map.put('f', 15);

        for (int i = 0; i < size; i++) {
            result *= 16;
            char cur = input.charAt(i);
            if (map.containsKey(cur)) {
                result += map.get(cur);
            } else {
                result += cur - '0';
            }
        }

        return result;
    }

    public static void main(String[] args) {
        Solution sol = new Solution();
        int res = sol.hexToDec("435fae");
        System.out.println(res);
    }
}