import java.util.ArrayList;

import java.util.Scanner;

public class MumbleRap {

public static void main(String[] args) {

Scanner sc = new Scanner(System.in);

sc.nextLine();

System.out.println(mumbleRap(sc.nextLine()));

sc.close();

}

public static int mumbleRap(String word) {

int max = 0, start, end;

ArrayList<Integer> list = new ArrayList<>();

for (int i = 0; i < word.length(); i++) {

if(!Character.isDigit(word.charAt(i))){

continue;

}

else{

start = i;

while(i < word.length() && Character.isDigit(word.charAt(i))){

i++;

}

end = i;

}

list.add(Integer.parseInt(word.substring(start, end)));

}

max = findMax(list);

return max;

}

private static int findMax(ArrayList<Integer> list) {

int max = 0;

for (Integer integer : list) {

if(integer > max) max = integer;

}

return max;

}

}