#include <bits/stdc++.h>
using namespace std;
const double eps = 0.000001;
int main() {
  ios_base::sync_with_stdio(0);
  cin.tie(0);
  int n, m;
  while (cin >> n >> m) {
    if ((m == 0 || m == 1) && n) {
      cout << "no" << endl;
      continue;
    }
    n -= m - 1;
    if (n < 0 || (n & 1))
      cout << "no" << endl;
    else
      cout << "yes" << endl;
  }
}
