#include<iostream>
#include<stdlib.h>
#include<cstdio>
#include<queue>
#include<vector>
class node {
public:
  int num,Value;
};
node a[10001];
int b[10001];
void push(int m,node n) {
  a[m].num=n.num;
  a[m].Value=n.Value;
}
int main() {
  int n,maxx,m;m=0;
  maxx=0;
  std::string s;
  std::cin>>n;
  std::cin>>s;
  for(int i=0;i<s.length();i++) {
      b[i+1]=s[i]-48;
  }
  for(int i=1;i<=s.length();i++) {
      if(b[i]!=b[i-1] and (i-1))
      {
        push(++m,(node){maxx,b[i-1]});
	maxx=0;
      }
      maxx++;
      if(i==1)
        continue;
  }
  push(++m,(node){maxx,b[s.length()]});
  for(int i=1;i<=m;i++)
    printf("%d%d",a[i].num,a[i].Value);
  getchar();
  exit(0);
}