{
TASK:edi
LANG:Pascal
}
var a:array[1..100000]of longint;
n,i,br,j,t:longint;
begin
readln(n);
for i:=1 to n do readln(a[i]);
for i:=1 to n do begin
for j:=1 to n-1 do if a[j]<a[j+1] then begin
t:=a[j]; a[j]:=a[j+1]; a[j+1]:=t; end; end;
for i:=1 to n-1 do begin
br:=0;
for j:=1 to n do if a[j]>=a[i] then br:=br+1;
if br>=a[i] then begin writeln(a[i]); break; end; end;
end.

