****************Наименьшая система счисления**************** http://acmp.ru/index.asp?main=task&id_task=315

minimum_notation.java

import java.io.*;
import java.util.*;

public class Main{ 
    
  public static void main(String[] argv) throws IOException,Exception{
    new Main().run();
  }
 
  public void run() throws IOException,Exception{
    BufferedReader  sc = new BufferedReader(new FileReader("input.txt"));   
    String[] str = sc.readLine().split("(?!^)");
    
    Map<String, Integer> dict = new HashMap();
    for (int i = 0; i < 10; i++) {
        if (i == 0 || i == 1) {
            dict.put(Integer.toString(i), 2);
        }else {
            dict.put(Integer.toString(i), i+1);
        }
    }
    int uppercase = 65;
    int lowercase = 97;
    for (int i = 11; i < 37; i++) {
        dict.put(Character.toString ((char) uppercase++), i);
        dict.put(Character.toString ((char) lowercase++), i);
    }
    
    int result = 0;
    for (String string : str) {
        if (string.matches("[^a-zA-Z0-9]")) {
            result = -1;
            break;
        }
        if (dict.containsKey(string)) {
            if (dict.get(string) > result) {
                result = dict.get(string);
            }
        }
    }
    PrintWriter pw = new PrintWriter(new File("output.txt"));
    pw.print(result);
    pw.close();
  }
}