#include<bits/stdc++.h>
using namespace std;
#define sz(v) (int)v.size()
#define all(v) begin(v), end(v)
#define compact(v) v.erase(unique(all(v)), end(v))
#define dbg(v) "[" #v " = " << (v) << "]"
#define file(name) if(fopen(name".inp", "r")) {freopen(name".inp", "r", stdin); freopen(name".out", "w", stdout); }
#define rep(i, l, r) for(int i = (l); i < (r); ++i)
using ll = long long;
using vi = vector<int>;
using vl = vector<long long>;
using ld = long double;
template<typename T>
bool minimize(T& a, const T& b){
if(a > b){
return a = b, true;
} return false;
}
template<typename T>
bool maximize(T& a, const T& b){
if(a < b){
return a = b, true;
} return false;
}
template<int dimension, typename T>
struct tensor : public vector<tensor<dimension - 1, T>> {
static_assert(dimension > 0, "Dimension must be positive !\n");
template<typename... Args>
tensor(int n = 0, Args... args) : vector<tensor<dimension - 1, T>> (n, tensor<dimension - 1, T>(args...)) {}
};
template<typename T>
struct tensor<1, T> : public vector<T> {
tensor(int n = 0, T val = T()) : vector<T>(n, val) {}
};
const int MAX = 6e5 + 5;
int n, m;
ll slope[MAX], intercept[MAX];
vector<pair<int, int>> adj[MAX];
priority_queue<ll> pq[MAX];
void convert(int i, ll x){
while(slope[i] > 1){
intercept[i] += pq[i].top();
--slope[i];
pq[i].pop();
}
ll p = pq[i].top(); pq[i].pop();
ll q = pq[i].top(); pq[i].pop();
pq[i].push(p + x);
pq[i].push(q + x);
intercept[i] -= x;
}
void dfs(int u){
for(auto [v, w] : adj[u]){
if(n + 1 <= v && v <= n + m){
//leaf
slope[v] = 1;
intercept[v] = -w;
pq[v].push(w);
pq[v].push(w);
} else{
//non-leaf
dfs(v);
convert(v, w);
}
slope[u] += slope[v];
intercept[u] += intercept[v];
if(sz(pq[u]) < sz(pq[v])){
swap(pq[u], pq[v]);
}
while(!pq[v].empty()){
pq[u].push(pq[v].top());
pq[v].pop();
}
}
}
int main(){
ios_base::sync_with_stdio(0);
cin.tie(0);
if(fopen("task.inp", "r")){
freopen("task.inp", "r", stdin);
freopen("task.out", "w", stdout);
}
cin >> n >> m;
for(int i = 2; i <= n + m; ++i){
int p, w;
cin >> p >> w;
adj[p].emplace_back(i, w);
}
dfs(1);
while(slope[1] > 0){
intercept[1] += pq[1].top();
--slope[1];
pq[1].pop();
}
cout << intercept[1] << '\n';
return 0;
}
