You are given a weighted undirected tree on
vertices and a list of
updates. Each update changes the weight of
one edge. The task is to output the diameter of the tree after each update.
(The distance between two vertices is the sum of the weights on the unique simple path that connects them. The
diameter is the largest of all those distances.)
Input Specification
The first line contains three space-separated integers
and
– the number of vertices in the tree, the number of updates and the limit on the weights of
edges. The vertices are numbered
through
.
Next,
lines describing the initial tree follow. The
-th of these lines contains three space-separated integers
meaning that initially, there is an edge between vertices
and
with weight
. It is guaranteed that these
lines describe a tree.
Finally,
lines describing queries follow. The
-th of these lines contains two space-separated integers
. These two integers are then transformed according to the following scheme:


where
is the result of the last query (initially
). Tuple
represents a query which takes the
-th edge from the input and sets its weight to
.
Output Specification
Output
lines. For each
, line
should contain the diameter of the tree after the
-th update.
Scoring
Subtask 1 (
points):
and 
Subtask 2 (
points):
and 
Subtask 3 (
points):
and the edges of the tree are exactly all valid edges of the form
(Hence,
the tree is a star centered at vertex
.)
Subtask 4 (
points):
, and the edges of the tree are exactly all valid edges of the forms
and
(Hence, if we were to root the tree at vertex
, it would be a balanced binary tree.)
Subtask 5 (
points): it is guaranteed that after each update a longest simple path goes through vertex 
Subtask 6 (
points): no additional constraints
Sample Input 1
Copy
4 3 2000
1 2 100
2 3 1000
2 4 1000
2 1030
1 1020
1 890
Sample Output 1
Copy
2030
2080
2050
Sample Input 2
Copy
10 10 10000
1 9 1241
5 6 1630
10 5 1630
2 6 853
10 1 511
5 3 760
8 3 1076
4 10 1483
7 10 40
8 2051
5 6294
5 4168
7 1861
0 5244
6 5156
3 3001
8 5267
5 3102
8 3623
Sample Output 2
Copy
6164
7812
8385
6737
6738
7205
6641
7062
6581
5155
Note
The first sample is depicted in the figure below. The left-most picture shows the initial state of the graph. Each
following picture depicts the situation after an update. The weight of the updated edge is painted green, and the
diameter is red.
The first query changes the weight of the 3rd edge, i.e.
, to
. The largest distance between any pair of
vertices is
– the distance between
and
.
As the answer is
, the second query is


Hence the weight of the edge
is changed to
. This causes the pair
to be the pair with the greatest
distance, namely
.
The third query is decoded as


As the weight of the edge
decreases to
, the most distant pair is suddenly
with
.
Comments