Mahesh leaves his house in the early morning and walks towards the east in such a way that his shadow forms behind him. By noon he walks 10 km and rests. In the afternoon, he walks towards the west in such a way that his shadow again forms behind him and till sunset he walks 6 km. After sunset, he turns left and walks 3 km to reach his friend Suresh's house. What is the minimum distance between Mahesh's house and Suresh's house?