import java.util.Scanner;

public class Solution {

    public static void main(String[] args) {


        Scanner sc = new Scanner(System.in);
        String len = sc.nextLine();
        String str = sc.nextLine();

        int blocks = 1;
        char temp;
        char prev = str.charAt(0);

        for(int i = 1; i < str.length(); i ++){
            temp = str.charAt(i);
            if(temp == prev){
                blocks++;
            }
            else{
                if(temp == '1'){
                    while(blocks != 1){
                        System.out.print(0);
                        blocks--;
                    }
                }
                else{
                    System.out.print(blocks);
                }
                blocks = 1;
            }
            prev = temp;
            if(i == str.length() - 1 && temp == '1'){
                System.out.print(blocks);
            }
            if(i == str.length() - 1 && temp == '0'){
                while(blocks != 1){
                    System.out.print(0);
                    blocks--;
                }
            }
        }

    }
}