/*
TASK: siuu
*/
#include <bits/stdc++.h>
using namespace std;
#define ll long long
#define N 400005
#define ff first
#define ss second
#define pb push_back
#define sz(s) (int)s.size()
#define rep(c, a, b) for(c = a; c <= b; c++)
ll n, t, a[6000][6000], b[6000][6000], answer, k, jogap;
void solve1(int x,int bal) {
bool tr = 0, tp = 0;
if(!bal) tr = 1;
ll ans = 0;
for(int i = 1; i <= n; i++) {
tp = tr;
for(int j = 1; j <= n; j++) {
if(tp == 0) b[i][j] = 0;
else b[i][j] = 1;
if(j % x == 0) tp = 1 - tp;
if(a[i][j]!=b[i][j]) ans++;
}
if(i % x == 0) tr = 1 - tr;
}
answer = min(ans,answer);
}
int main () {
ios::sync_with_stdio(0);cin.tie(0);
cin >> n >> k;
for(int i = 1; i <= k; i++) {
int x1, x2,y1,y2;
cin >> x1 >> y1 >> x2 >> y2;
if(x1 % 2 == y1 % 2) answer++;
else jogap++;
if(n >= 4e3) continue;
for(int j = x1; j <= x2; j++) {
for(int l = y1; l <= y2; l++) {
a[j][l] = 1;
}
}
}
if(n >= 4e3) {
cout << min(n/2 * n/2 - jogap + answer,(n + 1)/2 * (n + 1)/2 - answer + jogap) << '\n';
return 0;
}
answer = INT_MAX;
for(int i = 1; i * i <= n; i++) {
if(n % i == 0) {
solve1(i, 1);
solve1(i, 0);
if(i != 1){
solve1(n/i,1);
solve1(n/i,0);
}
}
}
cout << answer << '\n';
}
