one

var
    k, i, number, decytok, answer : integer;
begin
    readln (k);
    decytok := 10 + ((k - 1) div 2);
    if (k mod 2 = 0) then begin
        answer := decytok mod 10;
    end
    else
    begin
        answer := decytok div 10;
    end;
    writeln (answer);
end.