bzoj1303

首先找到b的位置x，要求满足b为中位数的数列
把比b大的设为1，比b小设为-1
则数列满足条件则x 左边的的和+x右边的和=0 
然后应该就很好搞了

var a,l,r,s:array[0..200010] of longint;
    i,n,m,x,k,ans:longint;
begin
  readln(n,m);
  for i:=1 to n do
  begin
    read(x);
    if x=m then k:=i
    else if x>m then a[i]:=1
    else a[i]:=-1;
  end;
  l[n]:=1;
  r[n]:=1;
  for i:=k-1 downto 1 do
  begin
    s[i]:=s[i+1]+a[i];
    inc(l[s[i]+n]);
  end;
  for i:=k+1 to n do
  begin
    s[i]:=s[i-1]+a[i];
    inc(r[s[i]+n]);
  end;
  for i:=0 to 2*n-1 do
    ans:=ans+l[i]*r[2*n-i];
  writeln(ans);
end.