#include <bits/stdc++.h>
using namespace std;
#define ll long long
#define ld long double
#define pb push_back
#define all(x) begin(x), end(x)
#define SZ(x) (int)(x).size()
mt19937 rng(chrono::steady_clock::now().time_since_epoch().count());
const int n0 = 300003;
int n, m;
vector <array <int, 2>> g[n0];
struct Fn {
int k = 0;
ll b = 0;
priority_queue <ll> slp;
void merge(Fn & f) {
while (!f.slp.empty()) {
slp.push(f.slp.top());
f.slp.pop();
}
k += f.k;
b += f.b;
}
void minimize() {
while (k > 0) {
k--;
b += slp.top();
slp.pop();
}
}
void add(int w) {
while (k > 1) {
k--;
b += slp.top();
slp.pop();
}
if (k < 0) return;
ll x0 = slp.top() + w;
slp.pop();
if (k == 1) {
ll x1 = slp.top() + w;
slp.pop();
slp.push(x1);
}
slp.push(x0);
b -= w;
}
};
Fn f[n0];
void merge(int x, int y) {
if (SZ(f[x].slp) < SZ(f[y].slp)) swap(f[x], f[y]);
f[x].merge(f[y]);
}
Fn cur;
void dfs(int v, int p) {
for (auto i : g[v]) {
int to = i[0], w = i[1];
if (to == p) continue;
dfs(to, v);
if (SZ(g[to]) == 0) {
while (!cur.slp.empty()) cur.slp.pop();
cur.slp.push(w), cur.slp.push(w);
cur.k = 1, cur.b = -w;
f[v].merge(cur);
} else {
f[to].add(w);
merge(v, to);
}
}
}
int main() {
ios_base::sync_with_stdio(false), cin.tie(NULL);
cin >> n >> m;
for (int i = 2; i <= n + m; i++) {
int x, w;
cin >> x >> w;
g[x].pb({i, w});
}
dfs(1, 1);
f[1].minimize();
cout << f[1].b;
}
