var n,ans,i,j,k:longint;

x,y,a:array[0..100000]of longint;

begin

read(n);

for i:=1 to n do read(a[i]);

x[n]:=n+1;y[n]:=n+1;

for i:=n-1 downto 1 do

begin

j:=i+1;

while ja[i] then break else j:=x[j];

x[i]:=j;

end;

for i:=n-1 downto 1 do

begin

j:=i+1;

while j