#include<bits/stdc++.h>
using namespace std;
#define f first
#define s second
typedef long long ll;
const int maxn = 3e5+5;
const int mod = 998244353;
const ll inf = 1e18;
int n, m;
ll W[maxn];
int hh[maxn], sz[maxn];
priority_queue<ll> pq[maxn];
vector<int> graph[maxn];
pair<ll, ll> func[maxn];
void ph(int x){
func[x].s+=pq[x].top();
pq[x].pop();
func[x].f--;
}
void add(int x, ll val){
func[x].s -= val;
pq[x].push(val);
func[x].f++;
}
void Union(int x, int d){
func[x].f += func[d].f;
func[x].s += func[d].s;
while(!pq[d].empty()){
pq[x].push(pq[d].top());
pq[d].pop();
}
}
void dfs(int x){
sz[x]++;
if(x > n){
func[x] = {1, -W[x]};
hh[x]=x;
pq[x].push(W[x]);
pq[x].push(W[x]);
}
else{
int bc = 0;
for(auto v: graph[x]){
dfs(v);
sz[x]+=sz[v];
if(sz[bc] < sz[v])bc = v;
}
int id = hh[bc];
hh[x] = id;
for(auto v: graph[x]){
if(v == bc)continue;
Union(id, hh[v]);
}
func[id].s+=W[x];
while(func[id].f > 1)ph(id);
ll p1 = pq[id].top();
ph(id);
ll p2 = pq[id].top();
ph(id);
add(id, p1+W[x]);
add(id, p2+W[x]);
}
//cout << x << " " << func[hh[x]].f << " " << func[hh[x]].s << "\n";
}
int main(){
ios::sync_with_stdio(false);
cin.tie(0);
cin >> n >> m;
for(int i = 2; i <= n+m; i++){
int x;
cin >> x >> W[i];
graph[x].push_back(i);
}
dfs(1);
ph(hh[1]);
cout << func[hh[1]].s;
}
