program m;
var a:array[1..4000] of integer;
    p:array[1..4000] of integer;
    x:array[1..4000] of integer;
    n,s,i,j,k,f,m:integer;
    begin
    read(n);
    for i:=1 to n do
    read(a[i]);
    read(s);
    for j:=1 to s do
    read(p[j]);
    read(k);
    for f:=1 to k do
    read(x[f]);m:=0;
for i:=1 to n do
        for j:=1 to s do
          for f:=1 to k do
          begin
           if (a[i]=p[j]) and (p[j]=x[f]) and (x[f]=a[i]) then
         m:=m+1;
         end;
         write(m);
         end.

Your algo has complexity O(n1*n2*n3) id est 4000*4000*4000= 6.4*10^10. It's too much operations for one half a second. Try to use other algo instead of linear search twice.