var us,a,b,i,n: integer;
    niz: array[1..1000] of integer;
begin
us:=0;
readln (n);
for i:=2 to (n) do
   read (niz[i]);
readln (niz[n+1]);
niz[1]:=1001;
niz[n+2]:=-5;
for i:=2 to (n+1) do
   begin
      if (niz[i-1]>=niz[i]) and (niz[i+1]>niz[i]) then a:=i;
      if (niz[i-1]<niz[i]) and (niz[i+1]<=niz[i]) then begin
                                                          b:=i;
                                                          if (niz[b]<>niz[a]) and ((niz[b]-niz[a]) > us) then us:=niz[b]-niz[a];
                                                        end;
   end;
writeln (us);

end.