bzoj 1207: [HNOI2004]打鼹鼠 （dp）

var
  n,m,i,j,ans:longint;
  x,y,time,f:array[..]of longint;

begin
  readln(n,m);
  for i:= to m do

    readln(time[i],x[i],y[i]);
  ans:=;
  for i:= to m do begin
    f[i]:=;
    for j:= to i- do
      if (time[i]-time[j]>=abs(x[i]-x[j])+abs(y[i]-y[j])) and (f[i]<f[j]+) then begin
        f[i]:=f[j]+;
        if f[i]>ans then ans:=f[i];
    end;
  end;
  writeln(ans);
end.