//#pragma GCC optimize("Ofast", "unroll-loops")
//#pragma GCC target("sse", "sse2", "sse3", "ssse3", "sse4")
#include <bits/stdc++.h>
#define all(a) a.begin(),a.end()
#define len(a) (int)(a.size())
#define mp make_pair
#define pb push_back
#define fir first
#define sec second
#define fi first
#define se second
using namespace std;
typedef pair<int, int> pii;
typedef long long ll;
typedef long double ld;
template<typename T>
bool umin(T &a, T b) {
if (b < a) {
a = b;
return true;
}
return false;
}
template<typename T>
bool umax(T &a, T b) {
if (a < b) {
a = b;
return true;
}
return false;
}
#ifdef KIVI
#define DEBUG for (bool _FLAG = true; _FLAG; _FLAG = false)
#define LOG(...) print(#__VA_ARGS__" ::", __VA_ARGS__) << endl
template <class ...Ts> auto &print(Ts ...ts) { return ((cerr << ts << " "), ...); }
#else
#define DEBUG while (false)
#define LOG(...)
#endif
const int max_n = 3e5 + 11, inf = 1000111222;
vector <pii> edge[max_n];
int n, m;
ll ans = 0;
bool del[max_n];
inline bool dfs (int v, int p = -1, bool gg = false) {
bool ok = v >= n || gg;
bool there = v >= n;
for (auto [to, len] : edge[v]) {
if (to == p) {
continue;
}
if (dfs(to, v, ok)) {
there = true;
if (ok) {
ans += len;
}
}
}
if (v >= n && !gg) {
del[v] = true;
}
return there;
}
bool need[max_n];
priority_queue <ll> q[max_n];
ll b[max_n];
int k[max_n];
inline void solve (int v, int p = -1) {
int mx = -1, big = -1, L = -1;
for (auto [to, len] : edge[v]) {
if (to == p) {
continue;
}
if (del[to]) {
need[v] = true;
if (umax(mx, 0)) {
big = to;
L = len;
}
}
else {
solve(to, v);
if (!need[to]) {
continue;
}
need[v] = true;
if (umax(mx, len(q[to]))) {
big = to;
L = len;
}
}
}
if (!need[v]) {
return;
}
assert(big != -1);
{
int to = big, len = L;
if (del[to]) {
b[v] -= len;
++k[v];
q[v].push(len);
q[v].push(len);
} else {
int to_del = k[to] - 1;
ll s = 0;
for (int i = 0; i < to_del; i++) {
s += q[to].top();
q[to].pop();
}
ll a2 = q[to].top() + len;
q[to].pop();
ll a1 = q[to].top() + len;
q[to].pop();
q[v].swap(q[to]);
q[v].push(a1);
q[v].push(a2);
b[v] += b[to] - len + s;
++k[v];
}
}
for (auto [to, len] : edge[v]) {
if (to == p || to == big) {
continue;
}
if (del[to]) {
b[v] -= len;
++k[v];
q[v].push(len);
q[v].push(len);
}
else {
if (!need[to]) {
continue;
}
int to_del = k[to] - 1;
ll s = 0;
for (int i = 0; i < to_del; i++) {
s += q[to].top();
q[to].pop();
}
ll a2 = q[to].top() + len;
q[to].pop();
ll a1 = q[to].top() + len;
q[to].pop();
while (!q[to].empty()) {
q[v].push(q[to].top());
q[to].pop();
}
q[v].push(a1);
q[v].push(a2);
b[v] += b[to] - len + s;
++k[v];
}
}
}
int main() {
// freopen("input.txt", "r", stdin);
// freopen("output.txt", "w", stdout);
ios_base::sync_with_stdio(0);
cin.tie(0);
cin >> n >> m;
for (int i = 1, p, c; i < n + m; i++) {
cin >> p >> c;
--p;
edge[p].pb({i, c});
edge[i].pb({p, c});
}
dfs(0);
solve(0);
while (k[0] > 0) {
b[0] += q[0].top();
q[0].pop();
--k[0];
}
assert(!q[0].empty());
cout << b[0] + ans << '\n';
}
