#pragma GCC optimize("O3")
#pragma GCC optimize("unroll-loops")
#include <bits/stdc++.h>
using namespace std;
#define pb push_back
#define all(a) a.begin(),a.end()
typedef long long ll;
typedef pair<int,int> pii;
typedef pair<ll,ll> pll;
typedef unsigned long long ull;
typedef vector<int> vi;
const int mxn = 6e5+1;
vector<pii> g[mxn];
priority_queue<ll> pq[mxn];
ll val[mxn];
void dfs(int u = 1, int col = 0){
int mx = 0;
for(auto [v,c] : g[u]){
dfs(v,c);
if((int) pq[mx].size() < (int) pq[v].size())
mx = v;
}
if(mx==0){
pq[u].push(col);
pq[u].push(col);
val[u] = col;
return;
}
pq[u].swap(pq[mx]);
val[u] = val[mx];
for(auto [v,c] : g[u]) if(v!=mx){
while(!pq[v].empty()){
pq[u].push(pq[v].top());
pq[v].pop();
}
val[u] += val[v];
}
for(int i = 1; i < (int) g[u].size(); i++)
pq[u].pop();
val[u]+=col;
auto x = pq[u].top();
pq[u].pop();
pq[u].pop();
pq[u].push(x+col);
pq[u].push(x+col);
}
void solve(){
int n,m; cin >> n >> m;
for(int i = 2; i <= n+m; i++){
int p,c; cin >> p >> c;
g[p].emplace_back(pii{i,c});
}
dfs();
pq[1].pop();
while(!pq[1].empty()){
val[1] -= pq[1].top(); pq[1].pop();
}
cout << val[1];
}
signed main(){
cin.tie(0)->sync_with_stdio(0);
int t = 1;
// cin >> t;
while(t--){solve();}
}
