Long Binary Sequence

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문제 설명

예제2

문제

Bobo has a very very long binary sequence $s$ of length $n$ . All except $m$ positions $x\_1, x\_2, \dots, x\_m$ are $0$ (And $s\_{x\_1} = s\_{x\_2} = \dots = s\_{x\_m} = 1$ ).

Now bobo would like to know the number of distinct consecutive substrings of $s$ .

입력

The first line contains $2$ integers $n, m$ ( $1 \leq n \leq 10^9, 1 \leq m \leq \min\\{n, 1000\\}$ ).

The second line contains $m$ integers $x\_1, x\_2, \dots, x\_m$ ( $1 \leq x\_1 < x\_2 < \dots < x\_m \leq n$ ).

출력

A single integer denotes the number of distinct substrings.