var a:array[1..1000]of integer;

      n,i,j,dem,m1,m2,m3:integer;

      b:boolean;

begin

 readln(n);

for i:=1 to n do

 readln(a[i]);

m1:=0;m2:=0;m3:=0;dem:=0;

for i:=1 to n do begin

  b:=true;

  for  j:=2 to a[i]-1  do

   if (a[i] mod j=0)or(a[i]<=1) then begin b:=false; break; end;

  if b then ;

  if abs(a[i]-a[i+1])<m1 then beign m1:=abs(a[i]-a[i+1]); m2:=a[i]; m3:=a[i+1]; end;

 end;

writeln('co ',dem,' so nguyen to');

writeln(m2,' va ',m3,' co khoang cach lon nhat');

writeln('cac phan tu la phan tu chinh giua');

for i:=1 to n do begin

m2:=0;m3:=0;

 for j:=1 to n do 

  if a[i]>a[j] then m2:=m2+1 else if a[i]<a[j] then m3:=m3+1;

 if m2=m3 then writeln('phan tu thu ',i);

end;

readln;

end.