#include <bits/stdc++.h>
using namespace std;
const int inf = ~0u >> 1, MOD = 1e9 + 7;
char *TT, *mo, but[(1 << 15) + 2];
inline int rd() {
  int first = 0, c = 0, f = 1;
  for (; c < '0' || c > '9'; c = getchar()) f = c != '-';
  for (; c >= '0' && c <= '9'; c = getchar()) first = first * 10 + c - '0';
  return f ? first : -first;
}
char s[123465];
int main() {
  int n = rd();
  scanf("%s", s + 1);
  int first = 0;
  for (int i = (1), i_end = (n); i <= i_end; i++) {
    if (s[i] == '1')
      first++;
    else {
      if (first)
        printf("%d", first), first = 0;
      else
        putchar('0');
    }
  }
  if (first)
    printf("%d\n", first);
  else if (s[n] == '0') {
    putchar('0'), putchar('\n');
  }
}
