#include <bits/stdc++.h>
using namespace std;
long long read()
{
    long long x = 0, f = 1;
    char c = getchar();
    while (c < '0' || c > '9')
    {
        if (c = '-')
            f = -1;
        c = getchar();
    }
    while (c >= '0' && c <= '9')
    {
        x = x * 10 + c - '0';
        c = getchar();
    }
    return x*f;
}
void write(long long x)
{
    if (x == 0)
    {
        putchar('0');
        return;
    }
    if (x < 0)
        putchar('-'),x = -x;
    if (x > 9)
        write(x / 10);
    putchar(x % 10 + '0');
}
long long n,sn=1;
string s;
int main(){
    n=read();
    cin>>s;
    for(int i=1;i<=n;i++){
        if(s[i]==s[i-1]){
            sn++;
            continue;
        }
        if(s[i]!=s[i-1]||i==n){
            write(sn);
            cout<<s[i-1];
            sn=1;
        }
    }
}