#include <bits/stdc++.h>
using namespace std;
const int maxn = 2005;
const int inf = 1e9;
inline int read() {
  int x = 0, f = 1;
  char c = getchar();
  for (; !isdigit(c); c = getchar())
    if (c == '-') f = -1;
  for (; isdigit(c); c = getchar()) x = x * 10 + c - '0';
  return x * f;
}
char a[100];
int ans[100];
int main() {
  int n;
  n = read();
  scanf("%s", a);
  int cnt = 0;
  for (int i = n - 1; i >= 0; --i) {
    int ret = 0, zero = 0;
    if (a[i] == '1') {
      for (; a[i] == '1'; --i) ret++;
      ans[cnt++] = ret;
    } else {
      for (; a[i] == '0'; --i) ans[cnt++] = ret;
      i++;
    }
  }
  for (int i = cnt - 1; i >= 0; --i) printf("%d", ans[i]);
  return 0;
}
