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B. Xenia and Ringroad

time limit per test

2 secondsmemory limit per test

256 megabytesinput

standard inputoutput

standard outputXenia 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.

Input

The first line contains two integers *n* and *m* (2 ≤ *n* ≤ 10^{5}, 1 ≤ *m* ≤ 10^{5}). The second line contains *m* integers *a* _{1}, *a* _{2}, ..., *a* _{ m} (1 ≤ *a* _{ i} ≤ *n*). Note that Xenia can have multiple consecutive tasks in one house.

Output

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.

Examples

Input

4 3

3 2 3

Output

6

Input

4 3

2 3 3

Output

2

Note

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.

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