#include<bits/stdc++.h>
using namespace std;
#define ll long long
#define endl '\n'
const int N=1e5+10;
int n;
string s;
int ans[N];
int a[N];
int main(){
	cin>>n;
	cin>>s;
	for(int i=0;i<n;i++){
		if(s[i]=='0')
		ans[i+1]=0;
		if(s[i]=='1')
		ans[i+1]=1;
		if(s[i]=='2')
		ans[i+1]=2;
		if(s[i]=='3')
		ans[i+1]=3;
		if(s[i]=='4')
		ans[i+1]=4;
		if(s[i]=='5')
		ans[i+1]=5;
		if(s[i]=='6')
		ans[i+1]=6;
		if(s[i]=='7')
		ans[i+1]=7;
		if(s[i]=='8')
		ans[i+1]=8;
		if(s[i]=='9')
		ans[i+1]=9;
	}
	ll cnt=1;
	ll x=1;
	for(int i=1;i<=n;i++){
		if(i==n){
			a[x]=cnt;
			x++;
			a[x]=ans[i];
			break;
		}
		if(ans[i]==ans[i+1])
		cnt++;
		else{
			if(cnt==1000){
				a[x]=1;
				x++;
				a[x]=0;
				x++;
				a[x]=0;
				x++;
				a[x]=0;
				x++;
			}
			else if(cnt>99){
				a[x]=cnt/100;
				x++;
				a[x]=cnt/10%10;
				x++;
				a[x]=cnt%10;
				x++;
			}
			else if(cnt>9){
				a[x]=cnt/10;
				x++;
				a[x]=cnt%10;
				x++;
			}
			else{
		        a[x]=cnt;
		        x++;
		    }
			cnt=1;
			a[x]=ans[i];
			x++;
		}
	}
	for(int i=1;i<=x;i++)
	cout<<a[i];
	return 0;
}