#include <bits/stdc++.h>
using namespace std;
#define ll long long
const int mxN=3e5;
int n, m, p[mxN];
vector<int> adj[mxN];
ll c[mxN], yi0[mxN], yi1[mxN];
vector<ll> pc[mxN];
int main() {
ios_base::sync_with_stdio(0);
cin.tie(0);
cin >> n >> m;
for(int i=1; i<n+m; ++i) {
cin >> p[i] >> c[i], --p[i];
adj[p[i]].push_back(i);
}
for(int i=1; i<n; ++i) {
if(adj[i].size()==1) {
c[adj[i][0]]+=c[i];
adj[p[i]].push_back(adj[i][0]);
}
}
for(int i=n+m-1; i>=0; --i) {
if(adj[i].size()==1&&i)
continue;
if(i>=n) {
yi1[i]=-1;
pc[i].push_back(0);
pc[i].push_back(0);
}
for(int j : adj[i]) {
if(!yi0[j])
continue;
yi0[i]+=yi0[j];
yi1[i]+=yi1[j];
pc[i].insert(pc[i].end(), pc[j].begin(), pc[j].end());
}
sort(pc[i].begin(), pc[i].end());
pc[i].erase(pc[i].begin()-yi1[i]+1, pc[i].end());
pc[i][-yi1[i]-1]+=c[i];
pc[i][-yi1[i]]+=c[i];
yi0[i]+=c[i];
// cout << yi0[i] << " " << yi1[i] << endl;
}
ll ans=yi0[0];
for(int i=0; i<-yi1[0]; ++i)
ans+=(yi1[0]+i)*(pc[0][i]-(i?pc[0][i-1]:0));
cout << ans;
}
