public class Solution

     {

         public int MinDominoRotations(int[] A, int[] B)

         {

             var na = A.Length;

             var nb = B.Length;

             if (na != nb)

             {

                 return -;

             }

             var dic1 = new Dictionary<int, List<int>>();

             var dic2 = new Dictionary<int, List<int>>();

             for (var i = ; i <= ; i++)

             {

                 dic1.Add(i, new List<int>());

                 dic2.Add(i, new List<int>());

             }

             for (var i = ; i < na; i++)

             {

                 var a = A[i];

                 dic1[a].Add(i);

                 var b = B[i];

                 dic2[b].Add(i);

             }

             var minchanges = na;

             var find = false;

             for (var i = ; i <= ; i++)

             {

                 var top = dic1[i];

                 var bottom = dic2[i];

                 var temp = top.Union(bottom).Distinct();

                 if (temp.Count() == na)

                 {

                     minchanges = Math.Min(minchanges, na - Math.Max(top.Count(), bottom.Count()));

                     find = true;

                 }

             }

             return find ? minchanges : -;

         }

     }