#include<bits/stdc++.h>
#define fi first
#define se second
#define db double
#define U unsigned
#define P pair<int,int>
#define int long long
#define pb push_back
#define MP make_pair
#define all(x) x.begin(),x.end()
#define CLR(i,a) memset(i,a,sizeof(i))
#define FOR(i,a,b) for(int i=a;i<=b;i++)
#define ROF(i,a,b) for(int i=a;i>=b;i--)
#define debug(x) cerr<<#x<<'='<<x<<endl
#define MIN(a,b) ((a)<(b)?(a):(b))
#define MAX(a,b) ((a)>(b)?(a):(b))
#define gc getchar()
#define pc putchar
using namespace std;
inline int rd(){
    int x=0,f=1; 
    char ch=gc;
    while(ch<'0'||ch>'9'){if(ch=='-') f=-1;ch=gc;
    }
    while(ch>='0' && ch<='9') x=(x<<1)+(x<<3)+(ch^48),ch=gc;
    return x*f;
}
inline void wr(int x){
    if(x<0) x=-x;
    if(x>9) wr(x/10);
    pc((x%10)^48);
}
int n;
string s;
string ans;
int cnt=1;
signed main(){
    cin>>n;
    cin>>s;
    FOR(i,1,n){
        if(s[i]==s[i-1]){
            cnt++;
        }
        else{
            ans+=to_string(cnt);
            ans+=s[i-1];
            cnt=1;
        }
    }
    cout<<ans;
    return 0;
}