#include<cstdio>
int n,a,ans[2][1001],m;
int main()
{
//	freopen(".in","r",stdin);
//	freopen(".out","w",stdout);
	scanf("%d%1d",&n,&a);
	ans[0][0]=a;
	ans[1][0]=1;
	for(register int i=1;i^n;++i)
	{
		scanf("%1d",&a);
		if(a^ans[0][m])
		{
			ans[0][++m]=a;
			ans[1][m]=1;
		}
		else ++ans[1][m];
	}
	for(register int i=0;i<=m;++i)
		printf("%d%d",ans[1][i],ans[0][i]);
	return 0;
}