//#pragma GCC optimize("Ofast")
//#pragma GCC target("avx,avx2,fma")
//#pragma GCC target("sse,sse2,sse3,ssse3,sse4.1,sse4.2,sse4a,avx,avx2,popcnt,tune=native")
#include <bits/stdc++.h>
#include <ext/pb_ds/assoc_container.hpp>
using namespace __gnu_pbds;
using namespace std;
template <typename T> //order_of_key = menores, find_by_order = consultar indexado en 0, regresa iterador
using ordered_set = tree<T, null_type, less_equal<T>, rb_tree_tag, tree_order_statistics_node_update>;
using ll = long long;
using ld = long double;
using pii = pair<int, int>;
using pll = pair<ll, ll>;
using vll = vector<ll>;
using vii = vector<int>;
mt19937_64 rnd(chrono::steady_clock::now().time_since_epoch().count());
#define mid ((l+r)>>1)
#define f first
#define s second
#define pb push_back
#define MP make_pair
#define all(x) (x).begin(),(x).end()
#define inicio(x) (*(x).begin())
#define rinicio(x) (*(x).rbegin())
#define SZ(x) (int)(x.size())
const ll MAXN = (ll)3e5 + 5;
const ll MOD = (ll)1e9 + 7;
vector<pll> g[MAXN];
priority_queue<ll> pq[MAXN];
ll sz[MAXN];
void dfs1(int nodo = 1, int p = 0) {
sz[nodo] = 1;
for (auto &it : g[nodo]) {
if (it.f == p) continue;
dfs1(it.f, nodo);
sz[nodo] += sz[it.f];
}
return;
}
void dfs2(int nodo = 1, int p = 0, ll d = 0) {
pll bign = MP(-1, -1);
for (auto &it : g[nodo]) {
if (it.f == p) continue;
if (bign.f == -1 || sz[it.f] > sz[bign.f]) bign = it;
}
if (bign.f != -1) {
dfs2(bign.f, nodo, bign.s);
swap(pq[nodo], pq[bign.f]);
}
else {
pq[nodo].push(0);
pq[nodo].push(0);
}
for (auto &it : g[nodo]) {
if (it.f == p || it.f == bign.f) continue;
dfs2(it.f, nodo, it.s);
while (!pq[it.f].empty()) {
pq[nodo].push(pq[it.f].top());
pq[it.f].pop();
}
}
for (int i = 0; i < SZ(g[nodo]) - 2; i++) pq[nodo].pop();
ll a, b;
a = pq[nodo].top();
pq[nodo].pop();
b = pq[nodo].top();
pq[nodo].pop();
a += d;
b += d;
pq[nodo].push(a);
pq[nodo].push(b);
return;
}
void tc() {
ll N, M, ans = 0, pre = 0; cin >> N >> M;
for (int i = 2; i <= N + M; i++) {
ll a, p; cin >> a >> p;
g[i].pb(MP(a, p));
g[a].pb(MP(i, p));
ans += p;
}
g[0].pb(MP(1, 0));
g[1].pb(MP(0, 0));
dfs1();
dfs2();
vll v;
pq[1].pop();
while (!pq[1].empty()) {
v.pb(pq[1].top());
pq[1].pop();
}
reverse(all(v));
for (int i = 0; i < SZ(v); i++) {
ans -= (SZ(v) - i)*(v[i] - pre);
pre = v[i];
}
cout << ans << "\n";
return;
}
int main() {
ios_base::sync_with_stdio(0);cin.tie(0);
int t = 1;
//cin >> t;
for (int i = 1; i <= t; i++) {
tc();
}
return 0;
}
//checa tus constantes, n = 1? overflow?
