题解

#include <bits/stdc++.h>
using namespace std;
vector<int> a, v;
vector<vector<int>> reversed_graph;
vector<bool> visited;
void mark(int y) {
	if (visited[y]) { return; }
	visited[y] = true;
	for (int c : reversed_graph[y]) { mark(c); }
}
int min_in_cycle(int curr) {
	int y = a[curr];
	int z = a[y];
	while (y != z) {
		y = a[y];
		z = a[a[z]];
	}
	int min_v = v[y];
	y = a[y];
	while (y != z) {
		min_v = min(min_v, v[y]);
		y = a[y];
	}
	mark(y);
	return min_v;
}

int main() {
	int n;
	cin >> n;
	v.resize(n);
	a.resize(n);
	visited.resize(n);
	reversed_graph.resize(n);

	long long max_moos = 0;
	for (int i = 0; i < n; i++) {
		cin >> a[i] >> v[i];
		a[i]--;
		reversed_graph[a[i]].push_back(i);
		max_moos += v[i];
	}

	for (int i = 0; i < n; i++) {
		if (!visited[i]) { max_moos -= min_in_cycle(i); }
	}

	cout << max_moos << endl;
}