using System;

int idk = 0;

int[] idkk = new int[1000];

int[] wth = new int[19];

​

for (int i = 0; i < 1000; i++ ) {

    Console.WriteLine("Enter the "  + (i+1) + " number: ");

    idkk[i] = int.Parse(Console.ReadLine());

}

for ( int i = 0; i < 1000; i++ ) {

    for ( int n = 0; n < 1000; n++ ) {

        if (idkk[i] == idkk[n]) {

    }

}