var n, a1, b, MAX, i, s : integer;
c : array [1..100] of integer;
f : double;
begin
    readln (n, a1, b, MAX);
    for i:= 1 to n do
    begin
    c[0]:=a1;
    c[i]:= c[i-1]*b;
    end;

    repeat
    for i:= 1 to n do
    f:=MAX/c[i];
    until f < 1;
    writeln (i-1);
end.