Implementing MWC algorithm for Random generator

One of my professors in university told us to write a random generator. He said that this is the function : x[i] = (a*x[i-1] + c) Mod m and if your system is 64 bits number m is (2^63) - 1.

He wrote this pseudo code: (MWC algorithm)

a = 65539; x[0] = 65539; m = (2^63) -1;
x[i] = ax[i-1];
if x[i] < 0
    then  x[i] = x[i] + m;
    else R[i]  = x[i] /m;
end if

And I tried to implement it in c#. Here is code I have written :

  using System;
  using System.Collections.Generic;
  using System.Linq;
  using System.Text;
  using System.Threading.Tasks;

  namespace Random_Generator
  {
      class Program
      {
          static void Main(string[] args)
          {           
               float a = 65539;
               float[] x = new float[100];
               x[0] = 65539;
               float m = (float)  Math.Pow(2,63) - 1;
               for(int i = 1; i < 100; i++)
               {
                    x[i] = (a ) * x[i - 1];

                    if (x[i] < 0)
                        x[i] = x[i ] +  m;

                    Console.WriteLine("Random Number {0} is {1}", i, (float)(x[i]/m));
               }
         }
      }
 }

As He said it should generate m random unique numbers. But when I run this code only the first 62 numbers generate correctly. After that all of the numbers that are generated are infinite.

I really can't find the problem and I really need it.

Can any one please help me? Thanks in advance.