// Judges with GCC >= 12 only needs Ofast
// #pragma GCC optimize("O3,no-stack-protector,fast-math,unroll-loops,tree-vectorize")
// MLE optimization
// #pragma GCC optimize("conserve-stack")
// Old judges
// #pragma GCC target("sse4.2,popcnt,lzcnt,abm,mmx,fma,bmi,bmi2")
// New judges. Test with assert(__builtin_cpu_supports("avx2"));
// #pragma GCC target("avx2,popcnt,lzcnt,abm,bmi,bmi2,fma,tune=native")
// Atcoder
// #pragma GCC target("avx2,popcnt,lzcnt,abm,bmi,bmi2,fma")
/*
#include <ext/pb_ds/assoc_container.hpp>
#include <ext/pb_ds/tree_policy.hpp>
using namespace __gnu_pbds;
typedef tree<int,null_type,less<int>,rb_tree_tag,tree_order_statistics_node_update> ordered_set;
- insert(x),erase(x)
- find_by_order(k): return iterator to the k-th smallest element
- order_of_key(x): the number of elements that are strictly smaller
*/
#include<bits/stdc++.h>
using namespace std;
mt19937_64 rng(chrono::steady_clock::now().time_since_epoch().count());
uniform_real_distribution<> pp(0.0,1.0);
#define int long long
#define ld long double
#define pii pair<int,int>
#define piii pair<int,pii>
#define mpp make_pair
#define fi first
#define se second
const long long inf=1e18;
const int mod=998244353;
const int maxn=300005;
const int B=650;
const int maxs=655;
const int maxm=200005;
const int maxq=1000005;
const int maxl=25;
const int maxa=1000000;
const int root=3;
int power(int a,int n){
int res=1;
while(n){
if(n&1) res=res*a%mod;
a=a*a%mod;n>>=1;
}
return res;
}
const int iroot=power(3,mod-2);
const int base=101;
int n,m;
int c[maxn],p[maxn];
int a[maxn],b[maxn];
priority_queue<int> pq[maxn];
void merge(int u,int v){
a[u]+=a[v];b[u]+=b[v];
if((int)pq[u].size()<(int)pq[v].size()) pq[u].swap(pq[v]);
while(!pq[v].empty()){
pq[u].push(pq[v].top());
pq[v].pop();
}
}
void solve(){
cin >> n >> m;
for(int i=2;i<=n+m;i++) cin >> p[i] >> c[i];
for(int i=n+1;i<=n+m;i++){
a[i]=1;
b[i]=-c[i];
pq[i].push(c[i]);
pq[i].push(c[i]);
merge(p[i],i);
}
for(int i=n;i>=2;i--){
while(a[i]>1){
b[i]+=pq[i].top();
a[i]--;pq[i].pop();
}
int t0=pq[i].top();pq[i].pop();
int t1=pq[i].top();pq[i].pop();
pq[i].push(t0+c[i]);pq[i].push(t1+c[i]);
b[i]-=c[i];merge(p[i],i);
}
while(a[1]>0){
b[1]+=pq[1].top();
a[1]--;pq[1].pop();
}
cout << b[1] << '\n';
}
signed main(){
ios_base::sync_with_stdio(false);
cin.tie(NULL);cout.tie(NULL);
int test=1;//cin >> test;
while(test--) solve();
}
