#include <bits/stdc++.h>
#define ll long long
#define ld long double
#define vi vector<int>
#define vl vector<long long>
#define ff first
#define ss second
#define pii pair<int,int>
#define pll pair<long long, long long>
#define pb push_back
#define rep(i, b) for(int i = 0; i < (b); ++i)
#define rep2(i,a,b) for(int i = a; i <= (b); ++i)
#define rep3(i,a,b,c) for(int i = a; i <= (b); i+=c)
#define count_bits(x) __builtin_popcountll((x))
#define all(x) (x).begin(),(x).end()
#define siz(x) (int)(x).size()
#define forall(it,x) for(auto& it:(x))
using namespace std;
//mt19937 mt;void random(){mt.seed(chrono::time_point_cast<chrono::milliseconds>(chrono::high_resolution_clock::now()).time_since_epoch().count());}
//ll rand(ll a, ll b) {return a + (mt() % (b-a+1));}
const int INF = 1e9+50;
const ll INF_L = 1e18+40;
const ll MOD = 1e9+7;
struct dp
{
priority_queue<ll> points;
ll init_slope = 0;
void merge(dp other)
{
init_slope += other.init_slope;
while(!other.points.empty())
{
points.push(other.points.top());
other.points.pop();
}
}
void add_edge(ll x)
{
ll cur_slope = init_slope + siz(points);
ll opt_poz = 0;
ll prev = 0;
while(true)
{
ll cur = points.top();
prev = opt_poz;
opt_poz = cur;
cur_slope--;
// cout << opt_poz << " " << cur_slope << " slope\n";
points.pop();
if(cur_slope == -1)
{
break;
}
}
points.push(opt_poz+x);
points.push(prev+x);
}
};
vi graph[300'001];
ll edge[300'001];
dp ansdp[300001];
void dfs(int v)
{
if(siz(graph[v]) == 0)
{
ansdp[v].init_slope = -1;
ansdp[v].points.push(edge[v]);
ansdp[v].points.push(edge[v]);
}
else
{
bool was = 0;
forall(it,graph[v])
{
dfs(it);
if(!was)
{
was = 1;
ansdp[v] = ansdp[it];
}
else
{
if(siz(ansdp[it].points) > siz(ansdp[v].points))
{
swap(ansdp[v],ansdp[it]);
}
ansdp[v].merge(ansdp[it]);
}
}
if(v != 1) ansdp[v].add_edge(edge[v]);
}
}
int main()
{
ios_base::sync_with_stdio(0);cin.tie(0);cout.tie(0);
//random();
int n,m;
cin >> n >> m;
ll cur_ans = 0;
rep2(i,2,n+m)
{
int p;
cin >> p >> edge[i];
cur_ans += edge[i];
graph[p].pb(i);
}
dfs(1);
ll ans_ = cur_ans;
ll cur_slope = ansdp[1].init_slope;
ll prev_point = 0;
vi p;
while(!ansdp[1].points.empty())
{
p.pb(ansdp[1].points.top());
ansdp[1].points.pop();
}
reverse(all(p));
forall(it,p)
{
cur_ans += cur_slope * (it-prev_point);
prev_point = it;
cur_slope++;
ans_ = min(ans_,cur_ans);
}
cout << ans_;
}
