program pyramid;
 
var
    L, N,area, lato : 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);
    L := 0; area:=0;
    while area<=N do
                   begin
                    L:=L+1;
                    area:=area+L*L;
                    if area>N then continue;
                   end;
    WriteLn(L-1);
 
end.

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