#include<bits/stdc++.h>
using namespace std;
#define int long long
const int N = 3e5 + 1;
struct Data {
int a, b;
priority_queue<int> pq;
Data operator + (Data x) {
a += x.a;
b += x.b;
if (pq.size() < x.pq.size())
pq.swap(x.pq);
while (x.pq.size()) {
pq.push(x.pq.top());
x.pq.pop();
}
return *this;
}
} f[N];
vector<int> g[N];
signed main() {
ios_base::sync_with_stdio(0);
cin.tie(0); cout.tie(0);
int n; cin >> n;
int m; cin >> m;
vector<int> c(n + m + 1);
for(int i = 2 ; i <= n + m ; ++i) {
int p;
cin >> p;
cin >> c[i];
g[p].push_back(i);
}
function<void(int)> dfs = [&](int u) {
if (u > n) {
f[u].a = 1;
f[u].b = -c[u];
f[u].pq.push(c[u]);
f[u].pq.push(c[u]);
return;
}
for(int v : g[u])
dfs(v), f[u] = f[u] + f[v];
for(; f[u].a > 1 ;)
f[u].a--,
f[u].b += f[u].pq.top(),
f[u].pq.pop();
int x = f[u].pq.top() + c[u]; f[u].pq.pop();
int y = f[u].pq.top() + c[u]; f[u].pq.pop();
f[u].b -= c[u];
f[u].pq.push(x);
f[u].pq.push(y);
}; dfs(1);
cout << f[1].b + f[1].pq.top() << endl;
}
/*
4 6
1 5
2 5
2 8
3 3
3 2
3 3
2 9
4 4
4 3
*/
