#include <bits/stdc++.h>
using namespace std;

int main(){
    ios::sync_with_stdio(false);
    cin.tie(0);
    int n, m, p;
    cin >> n >> m;
    vector<int> b(n);
    iota(b.begin(), b.end(), 0);
    vector<long long> S(m);
    while(m--){
        cin >> p, p--;
        S[m] = b[p] < b[p + 1] ? ((long long)(b[p]) << 17) | b[p + 1] : ((long long)(b[p + 1]) << 17) | b[p];
        swap(b[p], b[p + 1]);
    }
    sort(S.begin(), S.end());
    S.erase(unique(S.begin(), S.end()), S.end());
    cout << S.size() << '\n';
}