CF339B Xenia and Ringroad

Xenia lives in a city that has $ n $ houses built along the main ringroad. The ringroad houses are numbered 1 through $ n $ in the clockwise order. The ringroad traffic is one way and also is clockwise. Xenia has recently moved into the ringroad house number 1. As a result, she's got $ m $ things to do. In order to complete the $ i $ -th task, she needs to be in the house number $ a_{i} $ and complete all tasks with numbers less than $ i $ . Initially, Xenia is in the house number 1, find the minimum time she needs to complete all her tasks if moving from a house to a neighboring one along the ringroad takes one unit of time.

The first line contains two integers $ n $ and $ m $ $ (2

Print a single integer — the time Xenia needs to complete all tasks. Please, do not use the %lld specifier to read or write 64-bit integers in С++. It is preferred to use the cin, cout streams or the %I64d specifier.

In the first test example the sequence of Xenia's moves along the ringroad looks as follows: $ 1→2→3→4→1→2→3 $ . This is optimal sequence. So, she needs 6 time units.