#include <bits/stdc++.h>
#define int long long
using namespace std;
const int N=300010;
int n, m, t, ans, p[N], c[N], a[N];
priority_queue<int> pq[N];
signed main() {
ios_base::sync_with_stdio(0), cin.tie(0);
cin>>n>>m;
for (int i=2; i<=n+m; i++) cin>>p[i]>>a[i], ans+=a[i], c[p[i]]++;
for (int i=n+m; i>=1; i--) {
if (i>n) pq[i].push(a[i]), pq[i].push(a[i]);
else {
for (int j=1; j<c[i]; j++) pq[i].pop();
int x=pq[i].top()+a[i]; pq[i].pop();
int y=pq[i].top()+a[i]; pq[i].pop();
pq[i].push(x), pq[i].push(y);
}
if (i==1) break;
if (pq[p[i]].size()<pq[i].size()) swap(pq[p[i]], pq[i]);
while (!pq[i].empty()) pq[p[i]].push(pq[i].top()), pq[i].pop();
}
while (pq[1].size()>1) {
int v=pq[1].top(); pq[1].pop(), v-=pq[1].top();
ans-=v*(t++);
}
cout<<ans-pq[1].top()*(t++);
return 0;
}
