while input >= 0 and index < 10 do
    begin
    read(input);
    array1[index] := input;
        index++
    end;

input:= 0; //to reset it

another while loop but for list2...

list 1: 1 list 2: -1
list 1: 2 list 2: 2
list 1: 3 list 2: 3
list 1: -1 list 2: 4

index:= 0;
readln (input);
while (input >= 0) and (index < 10) do
 begin
  inc (index);
  array2[index]:= input;
  readln (input)
 end;