{ NOTE: it is recommended to use this even if you don't understand the following code }

var
    N, S : LongInt;

begin
{
    uncomment the two following lines if you want to read/write from files
    assign(input,  'input.txt');  reset(input);
    assign(output, 'output.txt'); rewrite(output);
}

    ReadLn(N);

    S := 0;

    { INSERT YOUR CODE HERE }


    WriteLn(S);

end.