program sdf;
var n,n1,n2,n3,i,i1,i2,k,a:integer;
m,m1,m2,e:array[1..1000 ] of integer;
begin
    k:=1;
readln(n1);
For i:=1 to n1 do readln(m[i]);
readln(n2);
For i:=1 to n2 do readln(m1[i]);
readln(n3);
For i:=1 to n3 do readln(m2[i]);
For i:=1 to n1 do
for i1:=1 to n2 do
for i2:=1 to n3 do begin
if (m[i]=m1[i1]) and (m1[i1]=m2[i2]) and (m[i]+m1[i1]+m[i2]<>-3) Then begin
                                          e[k]:=m[i];
                                          k:=k+1;
                                          m[i]:=-1;
                                             m1[i1]:=-1;
                                             m2[i2]:=-1;
                                             end;
 end;


For i:=1 to k do begin
for i1:=i+1 to k do begin
if e[i]=e[i1] Then e[i1]:=-1;
end;
end;
For i:=1 to k-1 do begin
if e[i]<>-1 Then a:=a+1;
end;
writeln(a);
end.
 в ЧЕМ ошибка?

почитай руководство. возможно, ошибка лишь в том, что написал "program sdf;".

ставь read, а не readln