#include <bits/stdc++.h>
using namespace std;
int main() {
  int n;
  cin >> n;
  string s;
  cin >> s;
  int one = 0;
  for (int i = 0; i < n; ++i) {
    if (s[i] == '1')
      ++one;
    else
      cout << one, one = 0;
  }
  cout << one;
}
