#include <bits/stdc++.h>
using namespace std;
#define rep(i,a,b) for (int i=a; i<int(b); i++)
int main() {
int n,m;
cin >> n >> m;
vector<int>p(n+m);
vector<long long>c(n+m);
p[0]=-1;
c[0]=-1;
rep (i,1,n+m) {
cin >> p[i] >> c[i];
p[i]--; //0-indexed
}
if (n==1 && m<=100) {
rep (i,1,m+1) {
assert(p[i]==0);
}
sort(c.begin(),c.end());
long long goal=c[m/2+1];
long long ans=0;
rep (i,1,m+1) {
ans+=abs(goal-c[i]);
}
cout << ans << endl;
}
else {
//assume N+M <=300 and longest path <=300;
long long cost[n+m][301]; //This will be, for every node, cost[t] is cost to make that node a certain time t
vector<vector<int> > children (n);
rep (i,1,n+m) {
children[p[i]].push_back(i);
}
queue<int> ready;
int done[n]; //Says how many of intersection i's children are done
rep (i,0,n) done[i]=0;
rep (i,n,n+m) {
//Loop over all leafs, set costs
cost[i][0]=0; //All leafs are 0
rep (j,1,301) {
cost[i][j]=999999999;
}
done[p[i]]++;
if (done[p[i]]==children[p[i]].size()) {
ready.push(p[i]);
}
}
while (true) {
int curr =ready.front();
ready.pop();
rep (i,0,301) {
cost[curr][i]=0;
//calculate sum for all children
for (auto child:children[curr]) {
long long best=999999999;
rep (j,0,i+1) {
best=min(best,cost[child][j]+abs(i-j-c[child]));
}
cost[curr][i]+=best;
}
}
if (curr==0) break;
done[p[curr]]++;
if (done[p[curr]]==children[p[curr]].size()) ready.push(p[curr]);
}
long long best=999999999;
rep (i,0,301) {
best=min(best,cost[0][i]);
}
cout << best << endl;
}
}
