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

public class Solution {
    public int AnyToDec (String input, int k) {
        //considering valid string input
        if (input == null || input.equals("") || k > 36) {
            throw new IllegalArgumentException("input is not valid");
        }

        int result = 0;
        int size = input.length();
        Map<Character, Integer> map = new HashMap<Character, Integer>();
        int base = 10;
        for (int i = 0; i < k - 10; i++) {
            char cur = (char)('a' + i);
            map.put(cur, base++);
        }

        for (int i = 0; i < size; i++) {
            result *= k;
            char cur = input.charAt(i);
            if (map.containsKey(cur)) {
                result += map.get(cur);
            } else {
                if (cur >= '0' && cur < '9' && cur < (char)(k + '0')) {
                    result += cur - '0';
                } else {
                    throw new IllegalArgumentException("input is not valid");
                }
            }
        }

        return result;
    }

    public static void main(String[] args) {
        Solution sol = new Solution();
        int res = sol.AnyToDec("1000", 2);
        System.out.println(res);
    }
}