{$APPTYPE CONSOLE}
var i,j,n,s:integer;f:text;
a,b:array [1..1000] of integer;
begin
assign(f,'Liars.dat');reset(f);
readln(f,n);
for i:=1 to n do read(f,a[i]);
close(f);
s:=0;
for i:=1 to n do b[i]:=0;
for i:=1 to n do
for j:=1 to n do
if a[j]=i then inc(b[i]);
for i:=1 to n do
if b[i]=i then inc(s);
if s=1 then s:=0;
assign(f,'Liars.sol');rewrite(f);
write(f,s);close(f);
end.