What people recite having their right-hand on their forehead after every fajr salat?

After every salat in masjid, I often see that some people recite something putting their right-hands on their head or forehead and counts in another hand. What is that dua and where they have found it? If it really exists, then what is the benefit of reciting it and how many times should it be recite? Jajakallah.