#include <bits/stdc++.h>
using namespace std;
const int N = 2000;
int n;
char s[N];
string ans;
int cnt = 1;
int main() {
	cin >> n;
	cin >> (s + 1);
	s[n + 1] = 'z';
	for (int i = 2; i <= n + 1; i++) {
		if (s[i] == s[i - 1]) {
			cnt++;
		} else {
			int x = cnt;
			cnt = 1;
			vector<char> v;
			while (x) {
				v.push_back(char(x % 10 + '0'));
				x /= 10;
			}
			for (int i = v.size() - 1; i >= 0; i--) {
				ans += v[i];
			}
			ans += s[i - 1];
		}
	}
	cout << ans;
	return 0;
}