#include<bits/stdc++.h>
#define lf double
#define ll long long
#define cc pair<char,char>
#define ull unsigned ll
#define ii pair<int,int>
#define li pair<ll,int>
#define iii pair<int,ii>
#define iiii pair<ii,ii>
#define iiii2 pair<int,iii>
#define lii pair<ll,ii>
#define lolo pair<ll,ll>
#define heap priority_queue
#define mp make_pair
#define st first
#define nd second
#define pb push_back
#define pf push_front
#define ppb pop_back
#define ppf pop_front
#define all(x) x.begin(),x.end()
#define len(x) strlen(x)
#define sz(x) (int) x.size()
#define orta ((bas+son)/2)
#define min3(x,y,z) min(min(x,y),z)
#define max3(x,y,z) max(max(x,y),z)
#define umin(x,y) x=min(x,y)
#define umax(x,y) x=max(x,y)
#define dbgs(x) cerr<<(#x)<<" --> "<<(x)<<" "
#define dbg(x) cerr<<(#x)<<" --> "<<(x)<<endl;getchar()
#define MOD 1000000007
#define inf 100000000000000000
#define M 10000002
#define N 305
#define LOG 20
#define magic 100
#define KOK 250
#define EPS 0.0025
#define pw(x) ((1ll)<<(x))
#define PI 3.1415926535
using namespace std;
int n,m,x,y;
ll ans,dp[N][N],sum[N];
vector<ii> v[N];
void dfs(int node,int ue) {
for(ii i:v[node]) dfs(i.st,i.nd);
memset(sum,0,sizeof(sum));
if(node>n) {
for(int i=1;i<N;i++) sum[i]=inf;
}
else {
for(ii i:v[node]) {
for(int cst=0;cst<N;cst++) sum[cst]+=dp[i.st][cst];
}
}
for(int i=0;i<N;i++) {
if(node==1) {
dp[node][i]=sum[i];
continue ;
}
dp[node][i]=inf;
for(int j=0;j<=i;j++) {
umin(dp[node][i],sum[j]+abs(ue-(i-j)));
}
}
}
int main() {
#if 0
freopen("input.txt","r",stdin);
#endif
scanf("%d %d",&n,&m);
for(int i=2;i<=n+m;i++) {
scanf("%d %d",&x,&y);
v[x].pb({i,y});
}
if(n==1) {
vector<int> c;
for(ii go:v[1]) c.pb(go.nd);
sort(all(c));
ll res=0;
for(int i=0;i<sz(c);i++) res+=abs(c[i]-c[sz(c)/2]);
printf("%lld",res);
return 0;
}
dfs(1,0);
ans=inf;
for(int i=0;i<N;i++) umin(ans,dp[1][i]);
printf("%lld",ans);
}
