#include <bits/stdc++.h>
using namespace std;
typedef long long ll;
typedef unsigned long long ull;
#define st first
#define nd second
#define pb push_back
#define all(a) a.begin(),a.end()
#define rep(a,b) for(int a = 0;a<b;a++)
const int inf = 1e9;
const ll infl = 1e18;
vector<vector<int>> gr;
vector<int> l;
vector<ll> mod;
vector<priority_queue<ll>> pq;
vector<ll> ans;
int comb(vector<int> v,int cmod)
{
int n = v.size();
vector<int> c;
pair<int,int> mx = {0,-1};
ll mx2 = -1;
for(int i : v)
{
if(pq[i].size() > mx.st)
{
mx = {pq[i].size(),i};
}
mx2 = max(mx2,pq[i].top()+mod[i]);
}
int r = mx.nd;
ll sum = 0;
for(int i : v)
{
if(r != i)
{
c.pb(i);
}
sum += ans[i] + mx2-(pq[i].top()+mod[i]);
}
for(int i : c)
{
while(!pq[i].empty())
{
pq[r].push((pq[i].top()+mod[i]-mod[r]));
pq[i].pop();
}
}
rep(i,n-1)
{
ll a = pq[r].top();
pq[r].pop();
sum -= (a-pq[r].top()) * (n-1-i);
}
ans[r] = sum;
mod[r] -= cmod;
ll b = pq[r].top();
pq[r].pop();
ll a = pq[r].top();
pq[r].pop();
pq[r].push(a+cmod);
pq[r].push(b+cmod);
return r;
}
int n,m;
int dfs(int v)
{
if(gr[v].size() > 0)
{
vector<int> cu;
for(int i : gr[v])
{
cu.pb(dfs(i));
}
return comb(cu,l[v]);
}
else
{
int c = v-n;
pq[c].push(l[v]);
pq[c].push(l[v]);
mod[c] = 0;
ans[c] = 0;
return c;
}
}
int main()
{
cin>>n>>m;
gr.resize(n+m);
l.resize(n+m);
l[0] = 0;
for(int i = 1;i<n+m;i++)
{
int p,c;
cin>>p>>c;
p--;
gr[p].pb(i);
l[i] = c;
}
ans.resize(m);
mod.resize(m);
pq.resize(m);
cout<<ans[dfs(0)]<<"\n";
}
