Program Task_6;
Var
a : array [1..10000] of integer;
i,n, sum: integer;
check : boolean;
Begin
sum:=0;
read(n);
check:=false;
for i := 1 to n do
       read(a[i]);

for i := 2 to n-1 do
    begin
    if ((a[i-1] < a[i]) and (a[i] > a[i+1])) then
          sum := sum +1;
    end;

    write(sum);

End.