#include <bits/stdc++.h>
//#include <ext/pb_ds/assoc_container.hpp>
#define x first
#define y second
#define ndl '\n'
#define mp make_pair
#define mt make_tuple
#define pb push_back
#define up_b upper_bound
#define low_b lower_bound
#define sz(x) (int)x.size()
#define all(x) x.begin(), x.end()
#define rall(x) x.rbegin(), x.rend()
using namespace std;
//using namespace __gnu_pbds;
//template<typename T> using indexed_set = tree <T, null_type, less<T>, rb_tree_tag, tree_order_statistics_node_update>;
mt19937_64 rng(chrono::steady_clock::now().time_since_epoch().count());//uniform_int_distribution<int> (l, r)
typedef long long ll;
typedef long double ld;
typedef unsigned int uint;
typedef unsigned long long ull;
typedef pair<ll, ll> pll;
typedef pair<int, int> pii;
typedef pair<int, ll> pil;
typedef pair<ll, int> pli;
typedef pair<int, ull> piu;
typedef vector<vector<int>> matrix;
const ll INF = 1e18 + 123;
const ld EPS = 1e-9;
const int inf = 1e9 + 123;
const int MOD = 1e9 + 7;
const int N = 3e5 + 123;
const int M = 1e6 + 123;
const double pi = 3.14159265359;
const int dx[] = {0, 0, 1, -1};
const int dy[] = {1, -1, 0, 0};
struct node{
ll a = 0, b = 0;
priority_queue<ll> q;
}dp[N];
vector<int> g[N];
int c[N];
void dfs(int v){
if (g[v].empty()){
dp[v].a = -1;
dp[v].b = c[v];
dp[v].q.push(c[v]);
dp[v].q.push(c[v]);
return;
}
for (int to : g[v]){
dfs(to);
dp[v].a += dp[to].a;
dp[v].b += dp[to].b;
if (sz(dp[v].q) < sz(dp[to].q)){
swap(dp[v].q, dp[to].q);
}
while (!dp[to].q.empty()){
dp[v].q.push(dp[to].q.top());
dp[to].q.pop();
}
}
while (dp[v].a + sz(dp[v].q) > 1){
dp[v].q.pop();
}
ll x1 = dp[v].q.top();
dp[v].q.pop();
ll x2 = dp[v].q.top();
dp[v].q.pop();
dp[v].b += c[v];
dp[v].q.push(x1+c[v]);
dp[v].q.push(x2+c[v]);
}
void solve(){
int n, m;
cin >> n >> m;
for (int i = 2, p; i <= n+m; i++){
cin >> p >> c[i];
g[p].pb(i);
}
dfs(1);
vector<ll> v;
while (!dp[1].q.empty()) {
v.push_back(dp[1].q.top());
dp[1].q.pop();
}
v.pb(0);
for (int i = sz(v)-2; dp[1].a < 0; i--, dp[1].a++){
dp[1].b += (v[i] - v[i+1]) * dp[1].a;
}
cout << dp[1].b;
}
int main(){
#ifdef me
freopen("input.txt", "r", stdin);
freopen("output.txt", "w", stdout);
#endif
ios_base::sync_with_stdio(0);
cin.tie(0);
int t = 1;
//cin >> t;
for (int i = 1; i <= t; i++){
//cout << "Case #" << i << ": ";
solve();
}
#ifdef KAZAKH
// cout << endl << 1.0 * clock() / CLOCKS_PER_SEC << endl;
#endif
return 0;
}
