func_code_string: #include <bits/stdc++.h>   using namespace std;   const int N = 1e5 + 9, M = 3e5 + 9, OO = 0x3f3f3f3f;   const double EPS = 0.00000000001;   const int mod = 1000003;   int n, m, d[3005];   bool flage = 1;   int main() {     scanf( %d%d , &n, &m);     for (int i = 0; i < m; ++i) {       scanf( %d , d + i);       if (d[i] == 1 || d[i] == n) flage = 0;     }     sort(d, d + m);     int mx = min(1, m);     for (int i = 0, j = 1; j < m; ++j)       if (d[j] == d[j - 1] + 1)         mx = max(mx, j - i + 1);       else         i = j;     if (mx >= 3) flage = 0;     if (flage)       puts( YES );     else       puts( NO );     return 0;   }   