#include <bits/stdc++.h>
using namespace std;
int main() {
    int N,K;
    cin >> N >> K;
    vector<int>A(K);
    for(int i = 0; i < K; i++) {
        cin >> A[i];
    }
    bool ok = true;
    for(int i = 1; i < K; i++) {
        if(A[i] == A[i-1]+1) {
            if(A[i-1]%2 == 1) {
                ok = false;
            }
        }
    }
    cout << ((ok)?"Yes":"No") << endl;
}