#include<bits/stdc++.h>
#define int long long
#define endl "\n"
using namespace std;
string s;
string ans;
int k;
int n;
void fun(char x,int y)
{	int c=1;
	for(int i=y+1;i<n;i++){
		if(s[i]==x) {
		c++;	
		k++;
		}
		else{
			break;
		}
	}
	string c1;
	while(c!=0){
		char c2=c%10+'0';
		c1+=c2;
		c/=10;
	}
	string c2=c1;
	for(int i=c1.size()-1;i>=0;i--){
		c1[i]=c2[c1.size()-1-i];
	}
	ans+=c1;
	ans+=x;
}
signed main(){
	ios::sync_with_stdio(0);
	cin.tie(0),cout.tie(0);
	cin>>n;
	cin>>s;
	for(int i=0;i<n;){
		fun(s[i],i);
		i=k+1;
		k++;	
	}
	cout<<ans;
	return 0;
}
/*10
 1111111111
 
 */