using System.Collections.Generic;
static List<int> random_caches = new List<int>();
private static int GetNumeroConta()
int c = a.Next(10000, 99999);
while(random_caches.Contains(c)) c = a.Next(10000, 99999);
public static void Main()
for(int i = 0; i <= 50; i++) {
Console.WriteLine(GetNumeroConta());