#include #include #include #include #include #include #include #include #include #include #include #include #include #include #include #include #include #include #include #include #include #include #include #include #include #include using namespace std; using ll = long long; using P = pair; constexpr int INF = 1001001001; constexpr int mod = 1000000007; // constexpr int mod = 998244353; template inline bool chmax(T& x, T y){ if(x < y){ x = y; return true; } return false; } template inline bool chmin(T& x, T y){ if(x > y){ x = y; return true; } return false; } int main(){ ios::sync_with_stdio(false); cin.tie(nullptr); ll N; int K; cin >> N >> K; vector A(K); for(int i = 0; i < K; ++i) cin >> A[i]; if(K == 1){ cout << "Yes\n"; return 0; } if(A.back() > 1000){ for(int i = K - 2; i >= 0; --i){ if(A[i + 1] <= 1000){ K = i + 2; break; } int gap = A[i + 1] - A[i]; if(gap == 1 || gap == 3 || gap == 5){ cout << "No\n"; return 0; } } } vector ban(1010); for(int i = 0; i < K; ++i) ban[A[i]] = true; for(int i = 1000; i >= 2; --i){ if(!ban[i]) continue; if(ban[i + 1] && i - 3 > 0){ ban[i - 3] = true; } if(ban[i + 3] && i - 2 > 0){ ban[i - 2] = true; } if(ban[i + 5] && i - 1 > 0){ ban[i - 1] = true; } } if(ban[1]) cout << "No\n"; else cout << "Yes\n"; return 0; }