#include <bits/stdc++.h>
using namespace std;
#define int long long
int inf = 1e13;
int n, m;
int t[300005], c[300005];
vector<int> f[300005];
struct schema_pantei
{
int a = 0, b = 0;///cum arata la final
priority_queue<int> pq;///punctele unde se schimba
};
schema_pantei s[300005];
int cine[300005];
void join(int x, int y)
{
while (x != cine[x])
x = cine[x];
while (y != cine[y])
y = cine[y];
if (s[x].pq.size() < s[y].pq.size())
{
while (!s[x].pq.empty())
s[y].pq.push(s[x].pq.top()), s[x].pq.pop();
s[y].a += s[x].a;
s[y].b += s[x].b;
cine[x] = y;
}
else
{
while (!s[y].pq.empty())
s[x].pq.push(s[y].pq.top()), s[y].pq.pop();
s[x].a += s[y].a;
s[x].b += s[y].b;
}
}
void dfs(int nod)
{
if (f[nod].empty())
{
cine[nod] = nod;
s[nod].a = 1;
s[nod].b = -c[nod];
s[nod].pq.push(c[nod]);
s[nod].pq.push(c[nod]);
}
else
{
for (auto fiu : f[nod])
dfs(fiu);
cine[nod] = nod;
for (auto fiu : f[nod])
join(nod, fiu);
int nd = nod;///!!!
while (cine[nd] != nd)
nd = cine[nd];
while (s[nd].a > 1)
{
s[nd].b += s[nd].pq.top();
s[nd].pq.pop();
s[nd].a--;
}
if (s[nd].a != 1)
assert(false);
int sl1 = s[nd].pq.top();
s[nd].pq.pop();
int sl0 = s[nd].pq.top();
s[nd].pq.pop();
s[nd].pq.push(sl0 + c[nod]);
s[nd].pq.push(sl1 + c[nod]);
s[nd].b -= c[nod];
}
}
signed main()
{
ios_base::sync_with_stdio(false);
cin.tie(NULL);
cout.tie(NULL);
cin >> n >> m;
n += m;
for (int i = 2; i <= n; i++)
{
cin >> t[i] >> c[i];
f[t[i]].push_back(i);
}
dfs(1);
int nd = 1;
while (nd != cine[nd])
nd = cine[nd];
cout << s[nd].b + s[nd].pq.top();
return 0;
}
