#include<bits/stdc++.h>
#define maxn 300005
using namespace std;
typedef long long ll;
int n, m;
vector < pair < ll, ll > > g[maxn];
struct Set{
priority_queue < ll > q;
ll sum, cnt;
Set(ll _sum = 0, ll _cnt = 0) : sum(_sum), cnt(_cnt) {};
void add(ll c) {
ll a = q.top(); q.pop();
ll b = q.top(); q.pop();
a += c;
b += c;
q.push(a);
q.push(b);
sum -= c;
}
void shift(){
while (cnt > 1) {
ll ret = q.top(); q.pop();
cnt --;
sum += ret;
}
}
} tem[maxn];
Set* a[maxn];
Set* mix(Set* a, Set* b) {
if ((a -> q).size() < (b -> q).size())
swap(a, b);
a -> cnt += b -> cnt;
a -> sum += b -> sum;
while (!(b -> q).empty()) {
ll ret = (b -> q).top(); (b -> q).pop();
(a -> q).push(ret);
}
return a;
}
void dfs(int u) {
if (g[u].size() == 0) {
(a[u] -> q).push(0);
(a[u] -> q).push(0);
a[u] -> cnt = 1;
}
for (auto i : g[u]) {
int v = i.first;
ll c = i.second;
dfs(v);
a[v] -> add(c);
a[u] = mix(a[u], a[v]);
}
a[u] -> shift();
}
int main(){
#define TASK "ABC"
// freopen(TASK".inp", "r", stdin); freopen(TASK".out", "w", stdout);
ios_base::sync_with_stdio(0);
cin >> n >> m;
for (int i = 2; i <= n + m; ++i) {
int p, c;
cin >> p >> c;
g[p].push_back({i, c});
}
for (int i = 1; i <= n + m; ++i)
a[i] = &tem[i];
dfs(1);
cout << (a[1] -> sum + (a[1] -> q).top());
return 0;
}
