/********include********/
#include <cstdio>
#include <cstring>
#include <iostream>
#include <string>
#include <cmath>
#include <bitset>
#include <vector>
#include <map>
#include <set>
#include <queue>
#include <deque>
#include <algorithm>
#include <complex>
#include <unordered_map>
#include <unordered_set>
#include <random>
#include <cassert>
#include <fstream>
#include <utility>
#include <functional>
#define popcount __builtin_popcount
using namespace std;

/***/
//#include <iomanip>
//#include <cmath>
#include <bits/stdc++.h>


/********define********/

#define rep(i,x) for(long long i=0;i<x;i++)
#define repn(i,x) for(long long i=1;i<=x;i++)
#define rrep(i,x) for(long long i=x-1;i>=0;i--)
#define rrepn(i,x) for(long long i=x;i>1;i--)
#define REP(i,n,x) for(long long i=n;i<x;i++)
#define REPN(i,n,x) for(long long i=n+1;i<x;i++)

#define pr printf
#define re return
#define mod 1000000007
//#define mod 998244353
#define inf  INT_MAX//19桁
#define INF 1e18+5//19桁
const double PI=3.14159265358979323846;
#define fi first
#define se second
#define MAX(a,b) (((a)>(b))?(a):(b))
#define MIN(a,b) (((a)<(b))?(a):(b))
#define all(x) (x).begin(),(x).end()

typedef long long int ll;
typedef pair<long long, long long> P;

ll A,B,C,D,E,F,G,H,I,J,K,L,M,N,O,Q,R,S,T,U,V,W,X,Y,Z;
double dA,dB,dC,dD,dE,dF,dG,dH,dI,dJ,dK,dL,dM,dN,dO,dP,dQ,dR,dS,dT,dU,dV,dW,dX,dY,dZ;




int main()
{
	cin.tie(0);
	ios::sync_with_stdio(false);

	
	cin>>N>>K;
	vector<ll>v(K);
	ll flg,wk;
	flg=wk=0;
	
	rep(i,K){
		cin >> v[i];
	}
	rep(i,K-1){
		if(v[i+1]-v[i]==1 && v[i]%2!=0){
			flg=1;
		}
	}
	if(flg==1){
		puts("No");
	}
	else{
		puts("Yes");
	}
	re 0;
    
}