#include "bits/stdc++.h"
using namespace std;
//#include "atcoder/all"
//using namespace atcoder;
#define int long long
#define REP(i, n) for (int i = 0; i < (int)n; ++i)
#define RREP(i, n) for (int i = (int)n - 1; i >= 0; --i)
#define FOR(i, s, n) for (int i = s; i < (int)n; ++i)
#define RFOR(i, s, n) for (int i = (int)n - 1; i >= s; --i)
#define ALL(a) a.begin(), a.end()
#define IN(a, x, b) (a <= x && x < b)
template<class T>istream&operator >>(istream&is,vector<T>&vec){for(T&x:vec)is>>x;return is;}
template<class T>inline void out(T t){cout << t << "\n";}
template<class T,class... Ts>inline void out(T t,Ts... ts){cout << t << " ";out(ts...);}
template<class T>inline bool CHMIN(T&a,T b){if(a > b){a = b;return true;}return false;}
template<class T>inline bool CHMAX(T&a,T b){if(a < b){a = b;return true;}return false;}
constexpr int INF = 1e18;

signed main(){
	int N, K;
	cin >> N >> K;
	vector<int>a(K);
	cin >> a;
	set<int>st;
	set<int>used;
	REP(i, K) {
		st.insert(a[i]);
		used.insert(a[i]);
	}
	auto f = [&](int x) {
		vector<int>ret(5);
		REP(i, 5) if(used.find(x + i + 1) != used.end()) ret[i] = 1;
		return ret;
	};
	while(st.size() > 0) {
		int a = *st.rbegin();
		st.erase(prev(st.end()));
		if(a < 1) break;
		//out(a);
		auto tmp = f(a);
		int one = (tmp[0]);
		int two = (tmp[2]);
		int three = (tmp[4]);
		if(one) {
			st.insert(a - 3);
		}
		if(two) {
			st.insert(a - 2);
		}
		if(three) {
			st.insert(a - 1);
		}
		if(one && two && three) {
			out("No");
			return 0;
		}
		if(a == 1) {
			out("No");
			return 0;
		}

		used.insert(a);
	}
	out("Yes");
}