#include <bits/stdc++.h>
using namespace std;
int main(){
ios::sync_with_stdio(false); cin.tie(nullptr);
int n, k;
cin >> n >> k;
vector <int> x1(k+1), y1(k+1), x2(k+1), y2(k+1);
if(n > 1000){
int cnt1 = 0, cnt2 = 0, cnt3 = 0, cnt4 = 0;
for(int i = 1; i <= k; i++){
cin >> x1[i] >> y1[i] >> x2[i] >> y2[i];
if(x1[i] % 2 == 1){
if(y1[i] % 2 == 1) cnt1++;
else cnt2++;
}
if(x1[i] % 2 == 0){
if(y1[i] % 2 == 1) cnt3++;
else cnt4++;
}
}
int ans = ((((n+1)/2) * ((n+1)/2)) - cnt1) + ((((n)/2) * ((n)/2)) - cnt4) + (k-(cnt4+cnt1));
ans = min(((((n+1)/2) * ((n+1)/2)) - cnt2) + ((((n)/2) * ((n)/2)) - cnt3) + (k-(cnt2+cnt3)), ans);
cout << ans;
return 0;
}
vector <vector <int>> a(n+1, vector <int> (n+1,0)), dp(n+1, vector <int> (n+1,0));
for(int i = 1; i <= k; i++){
cin >> x1[i] >> y1[i] >> x2[i] >> y2[i];
for(int i1 = x1[i]; i1 <= x2[i]; i1++){
for(int j1 = y1[i]; j1 <= y2[i]; j1++){
a[i1][j1] = 1;
}
}
}
for(int i = 1; i <= n; i++){
for(int j = 1; j <= n; j++){
dp[i][j] = (dp[i-1][j] + dp[i][j-1] - dp[i-1][j-1] + a[i][j]);
}
}
vector <int> v;
for(int i = 1; i < n; i++){
if(n % i == 0){
v.push_back(i);
}
}
int ans = n*n;
for(auto x : v){
int y = 0, y1 = 0;
bool tr = 1;
for(int i = 1; i <= n; i += x){
int cnt = 0;
for(int j = 1; j <= n; j += x){
cnt++;
if(cnt % 2 == tr){
y1 += (dp[i+x-1][j+x-1] - dp[i-1][j+x-1] - dp[i+x-1][j-1] + dp[i-1][j-1]);
y += ((x*x) - (dp[i+x-1][j+x-1] - dp[i-1][j+x-1] - dp[i+x-1][j-1] + dp[i-1][j-1]));
}
else {
y += (dp[i+x-1][j+x-1] - dp[i-1][j+x-1] - dp[i+x-1][j-1] + dp[i-1][j-1]);
y1 += ((x*x) - (dp[i+x-1][j+x-1] - dp[i-1][j+x-1] - dp[i+x-1][j-1] + dp[i-1][j-1]));
}
}
tr = (1-tr);
}
ans = min(ans,y);
ans = min(ans,y1);
}
cout << ans;
}
