Mince Pie Madness Puzzle

One afternoon, Hungry Horace made a large number of mince pies for his Christmas party the following day. He left them to cool overnight.

During the night Horace's brother Boris came downstairs and divided the mince pies into four equal piles with one left over, which he ate. He also ate one of the four piles, then went back to bed.

Later on, Horace's sister Doris came downstairs and again divided the mince pies into four equal piles with one left over, which she ate. She also ate one of her four piles and returned to bed.

In the morning, Horace found 60 pies left. How many had he made?