#include <bits/stdc++.h>
using namespace std;
vector<int> fillvec(int size) {
  vector<int> ans;
  for (int i = 0; i < size; i++) {
    int temp;
    cin >> temp;
    ans.push_back(temp);
  }
  return ans;
}
int gcd(int a, int b) { return !a ? b : gcd(b % a, a); }
vector<long long> getdivisors(long long n) {
  vector<long long> ans;
  for (long long i = 1; i <= sqrt(n); i++) {
    if (n % i == 0) {
      if (n / i == i) {
        ans.push_back(i);
      } else {
        ans.push_back(i);
        ans.push_back(n / i);
      }
    }
  }
  return ans;
}
int main() {
  ios::sync_with_stdio(0);
  cin.tie(0);
  int l, cn = 0;
  string n, a;
  cin >> l >> n;
  for (int i = 0; i < l; i++) {
    if (n[i] == '1') {
      cn++;
    } else {
      a += '0' + cn;
      cn = 0;
    }
  }
  a += '0' + cn;
  cout << a << endl;
}
