#include <bits/stdc++.h>
#define rep(i,n) for(int i = 0; i < (n); ++i)
#define srep(i,s,t) for (int i = s; i < t; ++i)
#define drep(i,n) for(int i = (n)-1; i >= 0; --i)
using namespace std;
typedef long long int ll;
typedef pair<int,int> P;
#define yn {puts("Yes");}else{puts("No");}
#define MAX_N 200005

int main() {
    ll n, k;
    cin >> n >> k;
    ll a[k+1] = {};
    srep(i,1,k+1) cin >> a[i];

    rep(i,k){
        if(a[i+1]-a[i] > 100){
            ll diff = a[i+1]-a[i]-100;
            srep(j,i+1,k+1){
                a[j] -= diff;
            }
        }
    }

    int m = a[k] + 10;
    int dp[m] = {};
    srep(i,1,k+1){
        dp[a[i]] = 1;
    }
    drep(i,a[k]+1){
        int ng = 0;
        srep(j,1,4){
            if(dp[i+j]&&dp[i+j+3]) ng = 1;
        }
        if(ng) dp[i] = 1;
    }
    
    if(dp[1]==0)yn;
    return 0;
}