#include<iostream>
#include<cstdio>
#define F(i, l, r) for(int (i) = (l); (i) <= (r); (i)++)
#include<queue>
using namespace std;
char s[1003];
int f[1003];
queue<int>q;
int main() {
//	freopen("A.in","r",stdin);
//	freopen("A.out","w",stdout);
	int n; scanf("%d", &n);
	scanf("%s", s+1);
	F(i, 1, n) f[i] = 1;
	F(i, 2, n) {
		if(s[i]==s[i-1]) f[i] = f[i-1] + 1;
	}
	F(i, 1, n) {
		if(f[i] > f[i+1] || (f[i] == f[i+1] && f[i]== 1) || (i==n)) {
			q.push(f[i]);
			q.push((s[i]-'0'));
		}
	}
	while(!q.empty()) {
		printf("%d", q.front());
		q.pop();
	}
//	fclose(stdin);
//	fclose(stdout);
	return 0;
}