#include <bits/stdc++.h>
using namespace std;
template <class T>
inline void umax(T &a, T b) {
  if (a < b) a = b;
}
template <class T>
inline void umin(T &a, T b) {
  if (a > b) a = b;
}
template <class T>
inline T abs(T a) {
  return a > 0 ? a : -a;
}
template <class T>
inline T gcd(T a, T b) {
  return __gcd(a, b);
}
template <class T>
inline T lcm(T a, T b) {
  return a / gcd(a, b) * b;
}
long long modpow(long long a, long long n, long long temp) {
  long long res = 1, y = a;
  while (n > 0) {
    if (n & 1) res = (res * y) % temp;
    y = (y * y) % temp;
    n /= 2;
  }
  return res % temp;
}
long long p2(long long n) { return (1ll << n); }
long long getbit(long long j, long long i) { return ((i >> (j - 1ll)) & 1ll); }
long long ison(long long mask, long long pos) { return (mask & (1 << pos)); }
long long cbit(long long n) {
  long long k = 0;
  while (n) n &= (n - 1), k++;
  return k;
}
long long nbit(long long n) {
  long long k = 0;
  while (n) n /= 2, k++;
  return k;
}
long long mod = 1000000007;
int sgn(long long x) { return x < 0 ? -1 : !!x; }
const double eps = 1e-7;
const double pi = acos(-1.0);
inline void inc(long long &x, long long y) {
  x += y;
  if (x >= mod) x -= mod;
}
inline void dec(long long &x, long long y) {
  x -= y;
  if (x < 0) x += mod;
}
inline void chmax(long long &x, long long y) {
  if (y > x) x = y;
}
inline void mulm(long long &x, long long y) {
  x *= y;
  if (x >= mod) x -= mod;
}
long long xo(long long i) {
  if ((i & 3) == 0) return i;
  if ((i & 3) == 1) return 1;
  if ((i & 3) == 2) return i + 1;
  return 0;
}
vector<long long> tree[100005];
long long a[100005];
void build(long long node, long long l, long long r) {
  if (l == r) {
    tree[node].push_back(a[l]);
    return;
  }
  long long m = (l + r) / 2ll;
  build(node * 2, l, m);
  build(node * 2 + 1, m + 1, r);
  tree[node].resize(tree[node * 2].size() + tree[2 * node + 1].size());
  merge(tree[node * 2].begin(), tree[node * 2].end(),
        tree[node * 2 + 1].begin(), tree[node * 2 + 1].end(),
        tree[node].begin());
}
long long query(long long node, long long l, long long r, long long st,
                long long en, long long v) {
  if (l > en || r < st) return 0;
  if (l >= st && r <= en) {
    return tree[node].end() -
           lower_bound((tree[node]).begin(), (tree[node]).end(), v);
  }
  long long m = (l + r) / 2ll;
  return query(node * 2, l, m, st, en, v) +
         query(node * 2 + 1, m + 1, r, st, en, v);
}
int main() {
  long long t, n, k, m, j;
  cin >> n;
  long long lasz = 0, c = 0;
  for (long long i = 1; i <= n; i++) {
    char ch;
    cin >> ch;
    if (ch == '1')
      c++;
    else {
      cout << c;
      c = 0;
    }
  }
  cout << c;
}
