#include <iostream>
#include <set>
#include <vector>
#include <algorithm>
using namespace std;
using ll = long long;
using vi = vector<int>;
using vll = vector<ll>;
#define sz(x) int(x.size())
int main()
{
ios_base::sync_with_stdio(false);
cin.tie(NULL);
int N, M;
cin >> N >> M;
vi children[1+N];
vi P(1+N+M);
vll C(1+N+M);
for(int i = 2; i <= N+M; i++)
{
cin >> P[i] >> C[i];
children[P[i]].push_back(i);
}
C[1] = 0;
vector< multiset<ll>* > dp(1+N+M);
vi subtree(1+N+M, 0);
vi expcount(1+N+M, 0);
for(int i = N+1; i <= N+M; i++)
{
dp[i] = new multiset<ll>;
dp[i]->insert(C[i]);
dp[i]->insert(C[i]);
expcount[i] = 1;
subtree[i] = 1;
}
for(int u = N; u >= 1; u--)
{
subtree[u] = 1;
expcount[u] = 0;
int max_child = children[u][0];
for(int v: children[u])
{
subtree[u] += subtree[v];
expcount[u] += expcount[v];
if(subtree[v] > subtree[max_child]) v = max_child;
}
dp[u] = dp[max_child];
for(int v: children[u])
{
if(v == max_child) continue;
for(ll x: *dp[v]) dp[u]->insert(x);
}
while(int(dp[u]->size()) > expcount[u] + 1)
{
dp[u]->erase(dp[u]->find(*dp[u]->rbegin()));
}
// lp[u] += C[u];
ll x1 = *dp[u]->rbegin();
dp[u]->erase(dp[u]->find(x1));
ll x2 = *dp[u]->rbegin();
dp[u]->erase(dp[u]->find(x2));
dp[u]->insert(x1 + C[u]);
dp[u]->insert(x2 + C[u]);
}
dp[1]->erase(dp[1]->find(*dp[1]->rbegin()));
ll ans = 0;
for(int i = 2; i <= N+M; i++) ans += C[i];
ll currx = 0;
ll currslope = -expcount[1];
while(!dp[1]->empty())
{
ll newx = *dp[1]->begin();
dp[1]->erase(dp[1]->find(newx));
ans += (newx - currx) * currslope;
currslope++;
currx = newx;
}
// while(dp[1].begin() <)
cout << ans << '\n';
}
