/**
* code generated by JHelper
* More info: https://github.com/AlexeyDmitriev/JHelper
* @author win11905
*/
#include <bits/stdc++.h>
#define all(x) (x).begin(), (x).end()
#define vi vector<int>
#define iii tuple<int, int, int>
#define long long long
#define pii pair<int, int>
#define x first
#define y second
using namespace std;
const long MOD = 1e9+7, LINF = 1e18 + 1e16;
const int INF = 1e9+1;
const double EPS = 1e-10;
const int dx[4] = {-1, 0, 1, 0}, dy[4] = {0, 1, 0, -1};
const int N = 3e5+5;
class firework {
private:
int n, m, cost[N], sz[N];
int slope[N], pos[N];
long start[N];
vector<int> g[N];
priority_queue<long> Q[N];
void dfs(int u) {
sz[u] = 1;
for(int &v : g[u]) {
dfs(v);
sz[u] += sz[v];
if(sz[v] > sz[g[u][0]]) swap(v, g[u][0]);
}
if(g[u].empty()) {
pos[u] = u;
start[u] = cost[u], slope[u] = -1;
Q[pos[u]].emplace(cost[u]), Q[u].emplace(cost[u]);
return;
}
for(int v : g[u]) {
slope[u] += slope[v], start[u] += start[v];
if(v == g[u][0])
pos[u] = pos[v];
else while(!Q[pos[v]].empty()) {
Q[pos[u]].emplace(Q[pos[v]].top());
Q[pos[v]].pop();
}
}
long opt1 = -1, opt2 = -1;
while(slope[u] + (int)Q[pos[u]].size() >= 0) {
swap(opt1, opt2);
opt1 = Q[pos[u]].top(), Q[pos[u]].pop();
}
Q[pos[u]].emplace(opt1 + cost[u]), Q[pos[u]].emplace(opt2 + cost[u]);
start[u] += cost[u];
}
public:
void solve(istream& cin, ostream& cout) {
cin >> n >> m;
for(int i = 2, par; i <= n+m; ++i) {
cin >> par >> cost[i];
g[par].emplace_back(i);
}
dfs(1);
vector<long> vec;
while(!Q[pos[1]].empty()) vec.emplace_back(Q[pos[1]].top()), Q[pos[1]].pop();
vec.emplace_back(0);
reverse(all(vec));
for(int i = 1; slope[1]; ++i) {
start[1] += slope[1] * (vec[i] - vec[i-1]);
slope[1]++;
}
cout << start[1] << endl;
}
};
class Solver {
public:
void solve(std::istream& in, std::ostream& out) {
firework *obj = new firework();
obj->solve(in, out);
}
};
int32_t main() {
ios::sync_with_stdio(false);
cin.tie(0);
Solver solver;
std::istream& in(std::cin);
std::ostream& out(std::cout);
solver.solve(in, out);
return 0;
}
