#include <bits/stdc++.h>
using namespace std;
typedef long long LL;
constexpr int NMAX = 3e5 + 5;
struct SlopeTrick {
LL a, b;
priority_queue <LL> *H;
SlopeTrick () {
a = 0;
b = 0;
H = new priority_queue<LL>;
}
SlopeTrick operator += (SlopeTrick r) {
a += r.a;
b += r.b;
if (H->size() < r.H->size())
swap(H, r.H);
while (!r.H->empty()) {
H->push(r.H->top());
r.H->pop();
}
return *this;
}
};
int N, M;
int Dad[NMAX];
LL Cost[NMAX];
vector <int> G[NMAX];
void Read () {
ios_base::sync_with_stdio(false);
cin.tie(nullptr);
cin >> N >> M;
for (int i = 2; i <= N + M; ++ i ) {
cin >> Dad[i] >> Cost[i];
G[Dad[i]].push_back(i);
}
}
void Solve (int Node, SlopeTrick &ans) {
while (ans.a > 1) {
LL x = ans.H->top();
ans.H->pop();
-- ans.a;
ans.b += x;
}
LL slope_1 = ans.H->top();
ans.H->pop();
LL slope_0 = ans.H->top();
ans.H->pop();
ans.H->push(slope_0 + Cost[Node]);
ans.H->push(slope_1 + Cost[Node]);
ans.b -= Cost[Node];
}
void Dfs (int Node, SlopeTrick &ans) {
bool leaf = true;
for (auto it : G[Node]) {
SlopeTrick aux;
leaf = false;
Dfs(it, aux);
ans += aux;
}
if (leaf) {
ans.a = 1;
ans.b = -Cost[Node];
ans.H->push(Cost[Node]);
ans.H->push(Cost[Node]);
return;
}
if (Node == 1) return;
Solve(Node, ans);
}
int main () {
Read();
SlopeTrick ans;
Dfs(1, ans);
while (ans.a > 0) {
LL x = ans.H->top();
ans.H->pop();
ans.b += x;
-- ans.a;
}
cout << ans.b << '\n';
return 0;
}
