const n=20; m=100;
type ar=array[1..n] of integer;
procedure p1(var a:ar);
var i:integer;
begin
for i:=1 to n do begin
 a[i]:=random(m)+1;
 write(a[i],' ');
 end;
writeln;
end;
function kol(var a:ar):integer;
var c:array[1..m] of 0..1;
 i,k:integer;
begin
for i:=1 to m do c[i]:=0;
for i:=1 to n do c[a[i]]:=1;
k:=0;
for i:=1 to m do k:=k+c[i];
kol:=k;
end;
var a:ar;
begin
Randomize;
p1(a);
writeln('k=',kol(a));
end.

Пример работы программы:
59 65 27 64 45 46 64 94 39 27 51 16 91 9 23 91 55 57 27 27 
k=15