Codeforces Round 504 (rated, Div. 1 + Div. 2, based on VK Cup 2018 Final)
G
Pisces
Codeforces
3400
原题
← F→
翻译中…

A group of researchers are studying fish population in a natural system of lakes and rivers. The system contains $n$ lakes connected by $n - 1$ rivers. Each river has integer length (in kilometers) and can be traversed in both directions. It is possible to travel between any pair of lakes by traversing the rivers (that is, the network of lakes and rivers form a tree).

翻译中…

There is an unknown number of indistinguishable fish living in the lakes. On day $1$, fish can be at arbitrary lakes. Fish can travel between lakes by swimming the rivers. Each fish can swim a river $l$ kilometers long in any direction in $l$ days. Further, each fish can stay any number of days in any particular lake it visits. No fish ever appear or disappear from the lake system. Each lake can accomodate any number of fish at any time.

翻译中…

The researchers made several observations. The $j$-th of these observations is "on day $d_j$ there were at least $f_j$ distinct fish in the lake $p_j$". Help the researchers in determining the smallest possible total number of fish living in the lake system that doesn't contradict the observations.

翻译中…

Input

翻译中…

The first line contains a single integer $n$ ($1 \leq n \leq 10^5$) — the number of lakes in the system.

翻译中…

The next $n - 1$ lines describe the rivers. The $i$-th of these lines contains three integers $u_i$, $v_i$, $l_i$ ($1 \leq u_i, v_i \leq n$, $u_i \neq v_i$, $1 \leq l_i \leq 10^3$) — $1$-based indices of lakes connected by the $i$-th river, and the length of this river.

翻译中…

The next line contains a single integer $k$ ($1 \leq k \leq 10^5$) — the number of observations.

翻译中…

The next $k$ lines describe the observations. The $j$-th of these lines contains three integers $d_j$, $f_j$, $p_j$ ($1 \leq d_j \leq 10^8$, $1 \leq f_j \leq 10^4$, $1 \leq p_j \leq n$) — the day, the number of fish, and the lake index of the $j$-th observation. No two observations happen on the same day at the same lake simultaneously.

翻译中…

Output

翻译中…

Print one integer — the smallest total number of fish not contradicting the observations.

翻译中…

Note

翻译中…

In the first example, there could be one fish swimming through lakes $2$, $1$, and $4$, and the second fish swimming through lakes $3$, $1$, and $2$.

翻译中…

In the second example a single fish can not possibly be part of all observations simultaneously, but two fish swimming $2 \to 1 \to 4$ and $3 \to 1 \to 5$ can.

翻译中…

In the third example one fish can move from lake $1$ to lake $5$, others staying in their lakes during all time: two fish in lake $4$, six fish in lake $5$, one fish in lake $3$. The system of lakes is shown on the picture.

翻译中…

image

翻译中…

样例

Input #1
4
1 2 1
1 3 1
1 4 1
5
1 1 2
1 1 3
2 2 1
3 1 4
3 1 2
Output #1
2
InputCopy OutputCopy
Input #2
5
1 2 1
1 3 1
1 4 1
1 5 1
4
1 1 2
2 1 3
3 1 4
4 1 5
Output #2
2
InputCopy OutputCopy
Input #3
5
2 5 1
5 1 1
2 4 1
5 3 3
6
5 2 4
2 1 1
2 1 3
2 2 4
4 7 5
4 1 2
Output #3
10
InputCopy OutputCopy
题目信息
题号
1023G
时间限制
5 s
内存限制
512 MB
标签
数据结构
网络流
树

题面与样例版权归 Codeforces 及出题人所有;中文翻译由 AI 生成(CI 管线),如有出入请以原文为准。