#include <cmath>
#include <functional>
#include <fstream>
#include <iostream>
#include <vector>
#include <algorithm>
#include <string>
#include <set>
#include <map>
#include <list>
#include <time.h>
#include <math.h>
#include <random>
#include <deque>
#include <queue>
#include <unordered_map>
#include <unordered_set>
#include <iomanip>
#include <cassert>
#include <bitset>
#include <sstream>
#include <chrono>
#include <cstring>
#include <numeric>
using namespace std;
typedef long long ll;
signed main()
{
#ifdef ONPC
FILE* stream;
freopen_s(&stream, "input.txt", "r", stdin);
#else
ios::sync_with_stdio(0); cin.tie(0); cout.tie(0);
#endif
int __, n;
cin >> __ >> n;
n += __;
vector<vector<int>> g(n);
vector<int> up(n, 0);
vector<priority_queue<ll>> pqs(n);
for (int i = 1; i < n; i++)
{
int par;
cin >> par >> up[i];
par--;
assert(0 <= par && par < i);
g[par].push_back(i);
}
ll sol = 0;
for (int i = 0; i < n; i++)
{
sol += up[i];
}
for (int i = n - 1; i >= 0; i--)
{
if (g[i].empty())
{
pqs[i].push(up[i]);
pqs[i].push(up[i]);
continue;
}
for (auto& j : g[i])
{
if ((int)pqs[i].size() < (int)pqs[j].size())
{
swap(pqs[i], pqs[j]);
}
while (!pqs[j].empty())
{
pqs[i].push(pqs[j].top());
pqs[j].pop();
}
}
for (int s = 1; s <= (int)g[i].size() - 1; s++)
{
pqs[i].pop();
}
ll x = pqs[i].top() + up[i];
pqs[i].pop();
ll y = pqs[i].top() + up[i];
pqs[i].pop();
pqs[i].push(x);
pqs[i].push(y);
}
pqs[0].pop();
while (!pqs[0].empty())
{
sol -= pqs[0].top();
pqs[0].pop();
}
cout << sol << "\n";
return 0;
}
