// #pragma GCC optimize("Ofast")
// #pragma GCC targt("sse,sse2,sse3,ssse3,sse4,popcnt,abm,mmx,avx,avx2,fma")
// #pragma GCC optimize("unroll-loops")
#include "bits/stdc++.h"
// #include <ext/pb_ds/assoc_container.hpp>
// #include <ext/pb_ds/trie_policy.hpp>
// #include <ext/rope>
using namespace std;
// using namespace __gnu_pbds;
// using namespace __gnu_cxx;
#define li long long
#define ld long double
#define ii pair<int, int>
#define vi vector<int>
#define vvi vector<vi>
#define fi first
#define se second
#define mp make_pair
#define pb push_back
#define pf push_front
#define eb emplace_back
#define em emplace
#define ob pop_back
#define om pop
#define of pop_front
#define fr front
#define bc back
#define fori(i, a, b) for(int i = (int) (a); i <= (int) (b); ++i)
#define ford(i, a, b) for(int i = (int) (a); i >= (int) (b); --i)
#define all(x) begin(x), end(x)
#define sz(x) ((int)(x).size())
#define bitc __builtin_popcountll
mt19937 rng(chrono::steady_clock::now().time_since_epoch().count());
#define rand rng
#define endl '\n'
#define sp ' '
#define fastio() ios_base::sync_with_stdio(false); cin.tie(NULL); cout.tie(NULL);
void solve();
signed main() {
// freopen("output.out","w",stdout);
// fastio();
int tc = 1;
// cin >> tc;
fori(test, 1, tc) {
solve();
}
return 0;
}
const ld pi = 4 * atan(1.0), eps = 1e-9;
#define int long long
const int maxn = 1e6 + 5;
int n,m;
int p[maxn], cost[maxn];
multiset<int> func[maxn];
int f0[maxn];
vi g[maxn];
void print(int i) {
cout << f0[i] << endl;
for(int v: func[i]) cout << v << sp;
cout << endl;
}
void dfs(int i) {
// cout << i << sp << g[i].size() << endl;
if(i > n - m) {
f0[i] = cost[i];
fori(tt, 0, 1) func[i].em(cost[i]);
}
else {
assert(g[i].size());
for(int j: g[i]) {
dfs(j);
if(func[j].size() > func[i].size()) {
func[i].swap(func[j]);
}
for(int v: func[j]) {
func[i].em(v);
}
f0[i] += f0[j];
}
// cout <<i << sp << func[i].size() << endl;
fori(tt, 1, g[i].size() - 1) {
func[i].erase(prev(func[i].end()));
}
// cout << i << "// " ; //endl;
// print(i);
if(i > 1) {
int r = *prev(func[i].end()); func[i].erase(func[i].find(r));
int l = *prev(func[i].end()); func[i].erase(func[i].find(l));
l += cost[i];
r += cost[i];
func[i].em(l);
func[i].em(r);
f0[i] += cost[i];
}
}
// cout << i << ": " ; //endl;
// print(i);
}
void solve() {
cin >> n >> m;
n += m;
fori(i, 2, n) {
cin >> p[i] >> cost[i];
g[p[i]].eb(i);
}
// fori(i, 2, n) {
// cout << p[i] << sp << i << sp << cost[i] << endl;
// }
dfs(1);
int ans = f0[1];
// cout << "dsfdf" << ans << endl;
func[1].erase(prev(func[1].end()));
int nowslope = 0;
while(func[1].size()) {
nowslope++;
int nowpoint = *prev(func[1].end());
func[1].erase(prev(func[1].end()));
int nxtpoint = (func[1].size()? *prev(func[1].end()): 0);
ans -= nowslope * abs(nowpoint - nxtpoint);
}
// cout << "sdgfsdghdfhfhg" << ans << endl;
cout << ans << endl;
}
