#include <bits/stdc++.h>
#define endl '\n'
//#pragma GCC optimize("Ofast")
using namespace std;
using ll = long long;
using ld = long double;
using pii = pair < int, int >;
using pll = pair < ll, ll >;
const ll INF = 2e18;
const ll DIM = 300007;
const ld PI = 3.1415926535;
const int mod = 999999893;
class convexFunction {
public:
convexFunction() {
k = 0;
b = 0;
}
multiset < ll > x;
ll k, b;
};
void merge(multiset < ll >& v1, multiset < ll >& v2) {
for(auto x: v2) v1.insert(x);
}
void merge(convexFunction& f1, convexFunction& f2) {
if(f1.x.size() < f2.x.size()) swap(f1, f2);
f1.k += f2.k;
f1.b += f2.b;
merge(f1.x, f2.x);
f2.x.clear();
}
int n, m;
vector < int > v[DIM];
ll p[DIM], c[DIM];
convexFunction f[DIM];
void dfs(int val) {
if(v[val].size() == 0) {
f[val].x = {c[val], c[val]};
f[val].k = 1;
f[val].b = -c[val];
return;
}
for(auto to: v[val]) {
dfs(to);
merge(f[val], f[to]);
}
while(f[val].k > 1) {
f[val].k--;
f[val].b += *f[val].x.rbegin();
f[val].x.extract(*f[val].x.rbegin());
}
if(val == 1) return;
pair < ll, ll > tmp;
tmp.first = *f[val].x.rbegin();
f[val].x.extract(tmp.first);
tmp.second = *f[val].x.rbegin();
f[val].x.extract(tmp.second);
tmp.first += c[val];
tmp.second += c[val];
f[val].x.insert(tmp.first);
f[val].x.insert(tmp.second);
f[val].b -= c[val];
}
int main() {
cin.tie(0); cout.tie(0); ios_base::sync_with_stdio(0);
#ifdef IloveCP
freopen("input.txt", "r", stdin);
freopen("output.txt", "w", stdout);
#endif
cin >> n >> m;
for(int i = 2; i <= n + m; i++) {
cin >> p[i] >> c[i];
v[p[i]].push_back(i);
}
dfs(1);
cout << *f[1].x.rbegin() + f[1].b << endl;
return 0;
}
