4
0 3 2
0 100 100
1 1 1
2 75 80

2

此题贪心 贪最小的点，易证必最优解

Program energy;
const
   maxn=1000;
var
   n,i,j,ans:longint;
   f,e,w,num,hpos:array[0..maxn] of longint;
procedure swap(var a,b:longint);
var
   t:longint;
begin
   t:=a;a:=b;b:=t;
end;
function max(a,b:longint):longint;
begin
   if a>b then exit(a) else exit(b);
end;
function min(a,b:longint):longint;
begin
   if a<b then exit(a) else exit(b);
end;
procedure qsort(l,r:longint);
var
   i,j,m,p:longint;
begin
   i:=l;
   j:=r;
   m:=e[(l+r) div 2];
   repeat
      while (e[i]<m) do inc(i);
      while (e[j]>m) do dec(j);
      if (i<=j) then
      begin
         swap(e[i],e[j]);
         swap(f[i],f[j]);
         swap(w[i],w[j]);
         swap(num[i],num[j]);
         inc(i);dec(j);
      end;
   until i>j;
   if (l<j) then qsort(l,j);
   if (i<r) then qsort(i,r);

end;

procedure pour(x:longint);
var
   noww,i,j:longint;
begin
   noww:=maxlongint;
   i:=x;
   while (i<>0) do
   begin
      noww:=min(noww,w[i]);
      i:=hpos[f[i]];
   end;

   if (noww<e[x]) then exit;

   inc(ans);
   i:=x;
   while (i<>0) do
   begin
      dec(w[i],e[x]);
      i:=hpos[f[i]];
   end;
end;
begin
   readln(n);
   for i:=1 to n do
   begin
      read(f[i],e[i],w[i]);
      num[i]:=i;
   end;
   qsort(1,n);
   hpos[0]:=0;
   for i:=1 to n do hpos[num[i]]:=i;


//   for i:=1 to n do write(f[i],' ',e[i],' ',w[i]);

   ans:=0;
   for i:=1 to n do pour(i);
   writeln(ans);

end.