#include <bits/stdc++.h>
using namespace std;
const int INF = 1000000;
int main(){
int N, M;
cin >> N >> M;
vector<int> P(N + M), C(N + M);
for (int i = 1; i < N + M; i++){
cin >> P[i] >> C[i];
P[i]--;
}
vector<vector<int>> c(N + M);
for (int i = 1; i < N + M; i++){
c[P[i]].push_back(i);
}
vector<vector<int>> dp(N + M, vector<int>(301));
for (int i = N; i < N + M; i++){
dp[i][0] = 0;
for (int j = 1; j <= 300; j++){
dp[i][j] = INF;
}
}
for (int i = N - 1; i >= 0; i--){
for (int j : c[i]){
vector<int> dp2(301, INF);
for (int k = 0; k <= 300; k++){
for (int l = 0; k + l <= 300; l++){
dp2[k + l] = min(dp2[k + l], dp[j][k] + abs(C[j] - l));
}
}
for (int k = 0; k <= 300; k++){
dp[i][k] += dp2[k];
}
}
}
int ans = INF;
for (int i = 0; i <= 300; i++){
ans = min(ans, dp[0][i]);
}
cout << ans << endl;
}
