#include<bits/stdc++.h>
#define f(x, y) for(int i = x;i <= y;i++)
using namespace std;

const int M = 1e4 + 10;
int n, maxn, on;
int a[M];

int main()
{
    cin >> n;
    f(1, n) scanf("%1d", &a[i]);
    on = a[1];
    f(1, n)
    {
        if(on != a[i]) {
            cout << maxn << on;
            on = a[i];
            maxn = 1;
        }
        else maxn++;
    }
    cout << maxn << on;
    return 0;
}