#include <bits/stdc++.h>
using namespace std;
unordered_set<int> even;
unordered_set<int> odd;
vector<int> fat;
int arr[200005];
int check[200005] = {0};
int main() {
  int n, m;
  cin >> n >> m;
  for (int i = 1; i <= n; i++) cin >> arr[i];
  for (int i = 1; i <= n; i++) {
    if (arr[i] % 2 == 0) {
      if (even.find(arr[i]) == even.end())
        even.insert(arr[i]);
      else
        check[i] = 1;
    } else {
      if (odd.find(arr[i]) == odd.end())
        odd.insert(arr[i]);
      else
        check[i] = 1;
    }
  }
  int evencnt = even.size(), oddcnt = odd.size();
  for (int i = 1; i <= n && (evencnt > n / 2 || oddcnt > n / 2); i++) {
    if (check[i]) continue;
    if (arr[i] % 2 == 0 && evencnt > n / 2) {
      check[i] = 1;
      evencnt--;
    }
    if (arr[i] % 2 == 1 && oddcnt > n / 2) {
      check[i] = 1;
      oddcnt--;
    }
  }
  int evenremaining = n / 2 - evencnt;
  int oddremaining = n / 2 - oddcnt;
  for (int i = 1; i <= n; i++)
    if (check[i]) fat.push_back(i);
  int fatsize = fat.size();
  for (int i = 1; i <= m && (evenremaining || oddremaining); i++) {
    if (i % 2 == 0 && evenremaining && even.find(i) == even.end()) {
      arr[fat.back()] = i;
      fat.pop_back();
      evenremaining--;
      continue;
    }
    if (i % 2 && oddremaining && odd.find(i) == odd.end()) {
      arr[fat.back()] = i;
      fat.pop_back();
      oddremaining--;
      continue;
    }
  }
  if (fat.size())
    cout << -1 << endl;
  else {
    cout << fatsize << endl;
    for (int i = 1; i <= n; i++) cout << arr[i] << " ";
  }
}
