#include <bits/stdc++.h>
using namespace std;
typedef long long ll;
const int MAXN = 3e5 + 10;
ll n, m;
vector<pair<ll, ll>> adj[MAXN];
vector<ll> x;
void input() {
cin >> n >> m;
for (int i = 1; i < n + m; i++) {
ll u, w;
cin >> u >> w;
adj[--u].push_back({i, w});
x.push_back(w);
}
}
int main() {
ios::sync_with_stdio(false); cin.tie(0);
input();
sort(x.begin(), x.end());
ll v = x[(int)x.size() / 2], res = 0;
for (int i = 0; i < x.size(); i++)
res += abs(x[i] - v);
cout << res << endl;
return 0;
}
