1 #include <cstdio>
 2 #include <iostream>
 3 #define ll long long
 4 using namespace std;
 5 const int N=6e5+10;
 6 int n,m,tot,dis[N],d[N],fa[N],t[N];
 7 ll sum,w[N];
 8 struct tree{ ll v;int l,r; }tr[N];
 9 int merge(int x,int y)
10 {
11     if (!x||!y) return x^y;
12     if (tr[x].v<tr[y].v) swap(x,y);
13     tr[x].r=merge(tr[x].r,y);
14     if (dis[tr[x].l]<dis[tr[x].r]) swap(tr[x].l,tr[x].r);
15     dis[x]=dis[tr[x].r]+1;
16     return x;
17 }
18 int pop(int x){ return merge(tr[x].l,tr[x].r); }
19 int main()
20 {
21     scanf("%d%d",&n,&m);
22     for (int i=2;i<=n+m;i++) scanf("%d%d",&fa[i],&w[i]),sum+=w[i],d[fa[i]]++;
23     for (int i=n+m;i>=2;i--)
24     {
25         ll l=0,r=0;
26         if (i<=n)
27         {
28             while (--d[i]) t[i]=pop(t[i]);
29             l=tr[t[i]].v,t[i]=pop(t[i]),r=tr[t[i]].v,t[i]=pop(t[i]);
30         }
31         tr[++tot].v=l+w[i],tr[++tot].v=r+w[i],t[i]=merge(t[i],merge(tot-1,tot)),t[fa[i]]=merge(t[fa[i]],t[i]);
32     }
33     while (d[1]--) t[1]=pop(t[1]);
34     while (t[1]) sum-=tr[t[1]].v,t[1]=pop(t[1]);
35     printf("%lld",sum);
36 }