#include<bits/stdc++.h>
#define For(i,a,b) for(register int i=(a);i<=(b);++i)
#define Rep(i,a,b) for(register int i=(a);i>=(b);--i)
#define int long long
using namespace std;
inline int read()
{
    char c=getchar();int x=0;bool f=0;
    for(;!isdigit(c);c=getchar())f^=!(c^45);
    for(;isdigit(c);c=getchar())x=(x<<1)+(x<<3)+(c^48);
    if(f)x=-x;return x;
}
#define maxn 600005
#define inf 0x3f3f3f3f
int n,m,cnt,res;
int fa[maxn],deg[maxn],rt[maxn],w[maxn];

int dis[maxn],ls[maxn],rs[maxn],val[maxn];
int merge(int x,int y)
{
	if(!x||!y)return x|y;
	if(val[x]<val[y])swap(x,y);
	rs[x]=merge(rs[x],y);
	if(dis[ls[x]]<dis[rs[x]])swap(ls[x],rs[x]);
	dis[x]=dis[rs[x]]+1;
	return x;
}
inline int pop(int&x){
	return x=merge(ls[x],rs[x]);
}

signed main()
{
	dis[0]=-1;
	n=read(),m=read();
	For(i,2,n+m)
		fa[i]=read(),w[i]=read(),res+=w[i],deg[fa[i]]++;
	Rep(i,n+m,2){
		int l=0,r=0; //k=0 duan
		if(i<=n)
		{
			while(--deg[i]) pop(rt[i]);
			r=val[rt[i]],pop(rt[i]);
			l=val[rt[i]],pop(rt[i]);
		}
		val[++cnt]=w[i]+l;
		val[++cnt]=w[i]+r;
		rt[i]=merge(rt[i],merge(cnt,cnt-1));
		rt[fa[i]]=merge(rt[fa[i]],rt[i]);
	}
	while(deg[1]--) pop(rt[1]);
	while(rt[1])res-=val[rt[1]],pop(rt[1]);
	cout<<res;
	return 0;
}