#include <bits/stdc++.h>
using namespace std;
#define int long long
const int N = 310000;
int n, m, p[N], c[N];
vector<int> g[N];
multiset<int> st[N];
void dfs(int v) {
if (g[v].empty()) {
st[v].insert(c[v]);
st[v].insert(c[v]);
return;
}
int slope = 0;
for (int u : g[v]) {
dfs(u);
slope++;
if (st[u].size() > st[v].size())
st[u].swap(st[v]);
for (auto x : st[u])
st[v].insert(x);
st[u].clear();
}
while (slope > 1) {
st[v].erase(prev(st[v].end()));
slope--;
}
int r = *st[v].rbegin(); st[v].erase(prev(st[v].end()));
int l = *st[v].rbegin(); st[v].erase(prev(st[v].end()));
st[v].insert(l + c[v]);
st[v].insert(r + c[v]);
}
int32_t main() {
ios::sync_with_stdio(0); cin.tie(0);
cin >> n >> m;
n += m;
for (int i = 2; i <= n; i++) {
cin >> p[i] >> c[i];
g[p[i]].push_back(i);
}
dfs(1);
int ans = 0;
for (int i = 2; i <= n; i++)
ans += c[i];
int slope = st[1].size() - 1;
int pos = 0;
for (int k : st[1]) {
ans -= slope * (k - pos);
slope--;
pos = k;
}
cout << ans;
}
