Why WA 28?I don't understand.
Here is my code:
program gjkh;
var a,b,ch,n,i,kol,sh,fir,sec,thi:longint;
m:array[1..100001]of longint;
flag:boolean;
begin
read(a);readln(b);
n:=0;
while not seekeof do begin
read(ch);
  if (n=0)or(m[n]<>ch)then begin
  n:=n+1;
  m[n]:=ch;
  end;
end;
flag:=true;
kol:=1;
for i:=1 to n do begin
if (i=1)then fir:=m[i]
  else begin
    if (flag=true)then begin
    sec:=m[i];
    flag:=false;
    end
    else begin
    thi:=m[i];
      if ((thi-sec)*(sec-fir)>0)then begin
      fir:=sec;sec:=thi;
      end
      else begin
      fir:=thi;
      kol:=kol+1;
      flag:=true;
      end;
    end;
  end;
end;
writeln(kol);
end.

1 5
-100000 500000 -70000 800000 -80000
answ: 3

Edited by author 01.02.2010 18:44

Input numbers must not exceed 100000 by absolute value.

why is 3, because there are 4 intervals?