代码如下

#include <bits/stdc++.h>
using namespace std;
const int N = 305;
vector<int> tree[N];
int credit[N], dp[N][N];
int n, m;
void dfs(int u, int father) {
	dp[u][0] = 0;
	for (int i = 0; i < tree[u].size(); i++) {
		int v = tree[u][i];
		if(v!=father) {
			dfs(v,u);
			for (int j = m; j >= 1; j--) {
				for (int k = 1; k <= j; k++) {
					dp[u][j] = max(dp[u][j], dp[u][j - k] + dp[v][k]);
				}
			}
		}

	}
}
int main() {
	int pre, credit_i;
	cin >> n >> m;
	for (int i = 1; i <= n; i++) {
		
		cin >> pre >> credit_i;
		tree[pre].push_back(i);
		tree[i].push_back(pre);
		credit[i] = credit_i;
	}
	for (int i = 0; i <= n; i++) {
		dp[i][1] = credit[i];
	}
	dfs(1, -1);
	cout << dp[1][m] << endl;
}