#include <bits/stdc++.h>
using namespace std;
#define POPCOUNT(n) (__builtin_popcountll((n)))
#define CLZ(n) (__builtin_clzll((n)))
#define CTZ(n) (__builtin_ctzll((n)))
#define LOG(n) (63 - __builtin_clzll((n)))
#define BIT(n, i) (((n) >> (i)) & 1ll)
#define MASK(i) (1ll << (i))
#define FLIP(n, i) ((n) ^ (1ll << (i)))
#define ON(n, i) ((n) | MASK(i))
#define OFF(n, i) ((n) & ~MASK(i))
#define Int __int128
#define fi first
#define se second
typedef long long ll;
typedef unsigned long long ull;
typedef long double ld;
typedef pair<int, int> pii;
typedef pair<long long, long long> pll;
typedef pair<long long, int> pli;
typedef pair<int, long long> pil;
typedef vector<pair<int, int>> vii;
typedef vector<pair<long long, long long>> vll;
typedef vector<pair<long long, int>> vli;
typedef vector<pair<int, long long>> vil;
template <class T1, class T2> bool maximize(T1 &x, T2 y) {
if (x < y) {
x = y;
return true;
}
return false;
}
template <class T1, class T2> bool minimize(T1 &x, T2 y) {
if (x > y) {
x = y;
return true;
}
return false;
}
template <class T> void remove_duplicate(vector<T> &ve) {
sort (ve.begin(), ve.end());
ve.resize(unique(ve.begin(), ve.end()) - ve.begin());
}
mt19937_64 rng(chrono::high_resolution_clock::now().time_since_epoch().count());
template <class T1, class T2> T1 random(T1 l, T2 r) {
return uniform_int_distribution<T1>(l, r)(rng);
}
template <class T> T random(T r) {
return rng() % r;
}
const int N = 1e6 + 5;
const int MOD = 1e9 + 7;
const int inf = 1e9;
const long long INF = 1e18;
int n, m;
int c[N];
vector<int> adj[N];
struct Functions {
ll a, b;
priority_queue<int> points;
Functions() {}
} info[N];
void dfs(int u) {
if (adj[u].empty()) {
info[u].a = 1, info[u].b = -c[u];
info[u].points.emplace(c[u]);
info[u].points.emplace(c[u]);
return;
}
for (auto v : adj[u]) {
dfs(v);
info[u].a += info[v].a;
info[u].b += info[v].b;
if (info[v].points.size() > info[u].points.size())
swap(info[u].points, info[v].points);
while (!info[v].points.empty()) {
info[u].points.emplace(info[v].points.top());
info[v].points.pop();
}
}
while (info[u].a > 1) {
--info[u].a;
info[u].b += info[u].points.top();
info[u].points.pop();
}
int x = info[u].points.top(); info[u].points.pop();
assert(!info[u].points.empty());
int y = info[u].points.top(); info[u].points.pop();
info[u].points.emplace(x + c[u]);
info[u].points.emplace(y + c[u]);
info[u].b -= c[u];
}
signed main() {
ios_base::sync_with_stdio(false); cin.tie(NULL); cout.tie(NULL);
cin >> n >> m;
for (int i = 2; i <= n + m; ++i) {
int p; cin >> p >> c[i];
adj[p].emplace_back(i);
}
dfs(1);
while (info[1].a > 0) {
--info[1].a;
info[1].b += info[1].points.top();
info[1].points.pop();
}
cout << info[1].b << '\n';
return 0;
}
