#pragma GCC optimize("Ofast")
#include<bits/stdc++.h>
using namespace std;
#define pb push_back
#define sz(x) (int)(x.size())
const int mxn = 3e5 + 5;
inline char gc()
{
const static int SZ = 1 << 16;
static char buf[SZ], *p1, *p2;
if (p1 == p2 && (p2 = buf + fread(p1 = buf, 1, SZ, stdin), p1 == p2))
return -1;
return *p1++;
}
inline void rd() {}
template <typename T, typename... U>
inline void rd(T &x, U &...y)
{
x = 0;
bool f = 0;
char c = gc();
while (isdigit(c))
x = (x << 1) + (x << 3) + (c ^ 48), c = gc();
f && (x = -x), rd(y...);
}
template <typename T>
inline void prt(T x)
{
if (x > 9)prt(x / 10);
putchar((x % 10) ^ 48);
}
vector<int>adj[mxn];
int n, m, l[mxn];
inline priority_queue<long long> dfs(int v){
priority_queue<long long>pq;
if(v > n){
pq.push(l[v]), pq.push(l[v]);
return pq;
}
for(auto u : adj[v]){
auto pq2 = dfs(u);
if(sz(pq) < sz(pq2)) swap(pq, pq2);
while(sz(pq2)){
pq.push(pq2.top());
pq2.pop();
}
}
for(int i = 1; i < sz(adj[v]); i++){
pq.pop();
}
long long R = pq.top(); pq.pop();
long long L = pq.top(); pq.pop();
pq.push(l[v] + L), pq.push(l[v] + R);
return pq;
}
inline void solve(){
rd(n), rd(m);
long long sum = 0;
int a;
for(int i = 2; i <= n + m; i++){
rd(a), rd(l[i]);
sum += l[i];
adj[a].pb(i);
}
auto pq = dfs(1);
pq.push(0);
sum += pq.top();
while(sz(pq) > 1){
sum -= pq.top();
pq.pop();
}
prt(sum);
}
signed main(){
solve();
}
