#include <bits/stdc++.h>
using namespace std;
map<int, int> mp;
int main() {
  ios::sync_with_stdio(false);
  int n, m;
  cin >> n >> m;
  int a[n + 1];
  int ev = 2, od = 1;
  int tev = 0, tod = 0;
  int tot = 0;
  for (int i = 0; i < n; i++) {
    cin >> a[i];
    mp[a[i]]++;
    if (a[i] % 2 == 0)
      tev++;
    else
      tod++;
  }
  for (int i = 0; i < n; i++) {
    if (mp[a[i]] > 1) {
      if (a[i] % 2) {
        if (tod > tev) {
          while (mp[ev] != 0) ev += 2;
          if (ev > m) return cout << -1, 0;
          mp[ev] = 1;
          mp[a[i]]--;
          a[i] = ev;
          tev++;
          tod--;
          tot++;
        } else {
          while (mp[od] != 0) od += 2;
          if (od > m) return cout << -1, 0;
          mp[od] = 1;
          mp[a[i]]--;
          a[i] = od;
          tot++;
        }
      } else {
        if (tod < tev) {
          while (mp[od] != 0) od += 2;
          if (od > m) return cout << -1, 0;
          mp[od] = 1;
          mp[a[i]]--;
          a[i] = od;
          tev--;
          tod++;
          tot++;
        } else {
          while (mp[ev] != 0) ev += 2;
          if (ev > m) return cout << -1, 0;
          mp[ev] = 1;
          mp[a[i]]--;
          a[i] = ev;
          tot++;
        }
      }
    }
  }
  for (int i = 0; i < n; i++) {
    if (a[i] % 2) {
      if (tev < tod) {
        tot++;
        while (mp[ev] != 0) ev += 2;
        if (ev > m) return cout << -1, 0;
        mp[ev] = 1;
        a[i] = ev;
        tod--;
        tev++;
      }
    } else {
      if (tev > tod) {
        tot++;
        while (mp[od] != 0) od += 2;
        if (od > m) return cout << -1, 0;
        mp[od] = 1;
        a[i] = od;
        tod++;
        tev--;
      }
    }
  }
  cout << tot << endl;
  for (int i = 0; i < n; i++) cout << a[i] << " ";
  return 0;
}
