func_code_string: #include <bits/stdc++.h>   using namespace std;   const int N = 100000;   int p[N], u[N];   int main() {     int n, k;     cin >> n >> k;     for (int i = 1; i <= k; i++) {       int x;       cin >> x;       if (p[x] == 0) p[x] = i;       u[x] = i;     }     long long rez = 0;     for (int i = 1; i <= n; i++) {       if (p[i] == 0) {         if (i == 1 || i == n)           rez += 2;         else           rez += 3;       } else {         if (i < n && (p[i] > u[i + 1])) rez++;         if (i > 1 && (p[i] > u[i - 1])) rez++;       }     }     cout << rez;     return 0;   }   