#include <iostream>
#include <set>
using namespace std;
#define ll long long
#define ld long double
signed main(){
set<ll> unique;
for(int i = 0; i < 2020; i++){
ll x;
cin >> x;
unique.insert(x);
}
cout << unique.size();
}
const k = 2020;
var b: array [0 .. k - 1] of integer;
x, y, z: integer;
begin
for x := 0 to k - 1 do readln(b[x]);
z:= 0;
for x := 0 to k - 1 do
begin
y := 0;
while b[y] <> b[x] do y := y + 1;
if y = x then z := z + 1
end;
writeln(z)
end.
