VAR n,i,j,s,max,mm,pr1,pr:int64; a:array[1..500001] of int64;
Begin
Readln(n);
for i:=1 to n do
Begin
Read(a[i]);
end;
max:=-33231231241;
for i:=1 to n do
Begin
s:=a[i];
pr:=0;
if (s > max) then max:=s;
for j:=i + 1 to n do
Begin
pr:=pr + a[j]*s;
s:=s + a[j];
if (pr > max) then max:=pr;
end;
end;
Writeln(max);
Readln;
END.