// FUCKED UP FUCKED UP FUCKED UP FUCKED UP FUCKED UP
#include <bits/stdc++.h>
using namespace std;
#pragma GCC optimize("O2,no-stack-protector,unroll-loops,fast-math")
#define F first
#define S second
#define pb push_back
#define SZ(x) (ll)(x.size())
#define all(x) x.begin(),x.end()
#define MP make_pair
typedef long long ll;
typedef long double ld;
typedef pair<ll,ll> pll;
//mt19937 rng(chrono::steady_clock::now().time_since_epoch().count());
const ll maxn=3e5+10, maxm=5e4+10, lg=21, mod=998244353, inf=1e18;
#define pq priority_queue<ll>
ll n,m,w[maxn],rr;
vector<ll> g[maxn];
pq dff(ll v=0){
pq q;
if(v<n){
for(auto u:g[v]){
pq p=dff(u);
if(SZ(q)<SZ(p)) swap(p,q);
while(!p.empty()) q.push(p.top()), p.pop();
}
for(int i=1;i<SZ(g[v]);i++) q.pop();
ll x=q.top()+w[v]; q.pop();
ll y=q.top()+w[v]; q.pop();
q.push(x), q.push(y);
}
else q.push(w[v]), q.push(w[v]);
return q;
}
int main(){
ios_base::sync_with_stdio(0),cin.tie(0),cout.tie(0);
cin>>n>>m;
for(int i=1,x;i<n+m;i++){
cin>>x>>w[i]; rr+=w[i];
g[--x].pb(i);
}
pq q=dff();
ll p=q.top(); q.pop();
ll tt=0;
while(!q.empty()) rr-=tt++*(p-q.top()), p=q.top(), q.pop();
cout<<rr-tt*p;
return 0;
}
