import java.io.BufferedReader;
import java.io.IOException;
import java.io.InputStreamReader;
import java.nio.charset.StandardCharsets;
import java.util.*;

public class Main {
  /**
   * Iterate through each line of input.
   */
  public static void main(String[] args) throws IOException {
    InputStreamReader reader = new InputStreamReader(System.in, StandardCharsets.UTF_8);
    BufferedReader in = new BufferedReader(reader);
    String[] strNums;
    strNums = in.readLine().split(",[ ]*");
    int sequence[] = new int[strNums.length];

    int max = Integer.MIN_VALUE;
    for (int i = 0; i < strNums.length; ++i){
      sequence[i] = Integer.parseInt(strNums[i]);
      if (i - 1 > 0){
        int current = sequence[i] + sequence[i - 1];
        if (current > max){
            max = current;
        }
      }
    }

    System.out.println(max);

    // while ((line = in.readLine().split("\\s")) != null) {
    //   System.out.println(line);
    // }

    // //int  sequence[] =
  }
}