/*
// is short or still long ???
hollwo_pelw's template(short)
// Note : -Dhollwo_pelw_local
*/
#include <bits/stdc++.h>
// #include <ext/pb_ds/assoc_container.hpp>
// #include <ext/pb_ds/trie_policy.hpp>
// #include <ext/rope>
using namespace std;
// using namespace __gnu_pbds;
// using namespace __gnu_cxx;
void FAST_IO(string filein = "", string fileout = "", string fileerr = ""){
if (fopen(filein.c_str(), "r")){
freopen(filein.c_str(), "r", stdin);
freopen(fileout.c_str(), "w", stdout);
#ifdef hollwo_pelw_local
freopen(fileerr.c_str(), "w", stderr);
#endif
}
cin.tie(0), cout.tie(0) -> sync_with_stdio(0);
}
void Hollwo_Pelw();
signed main(){
#ifdef hollwo_pelw_local
FAST_IO("input.inp", "output.out", "error.err");
auto start = chrono::steady_clock::now();
#else
FAST_IO("hollwo_pelw.inp", "hollwo_pelw.out");
#endif
int testcases = 1;
// cin >> testcases;
for (int test = 1; test <= testcases; test++){
// cout << "Case #" << test << ": ";
Hollwo_Pelw();
}
#ifdef hollwo_pelw_local
auto end = chrono::steady_clock::now();
cout << "\nExcution time : " << chrono::duration_cast<chrono::milliseconds> (end - start).count() << "[ms]" << endl;
#endif
return 0;
}
#define int long long
const int N = 1e5 + 5;
struct rect_t {
int x1, y1, x2, y2;
rect_t(int _x1 = 0, int _y1 = 0, int _x2 = 0, int _y2 = 0)
: x1(_x1), y1(_y1), x2(_x2), y2(_y2) {}
} a[N];
int n, m;
inline int get(int i, int k) {
return min(i % (2 * k), k) + i / (2 * k) * k;
}
inline int solve(int k) {
int cnt = n * n / (k * k);
int res = (cnt / 2) * (k * k);
// cout << "solve " << k << '\n';
for (int i = 1; i <= m; i++) {
auto [x1, y1, x2, y2] = a[i];
// cout << x1 << ' ' << y1 << ' ' << x2 << ' ' << y2 << '\n';
int H = x2 - x1 + 1;
int W = y2 - y1 + 1;
int tot = H * W;
// cout << H << ' ' << W << '\n';
int h = get(x2, k) - get(x1 - 1, k);
int w = get(y2, k) - get(y1 - 1, k);
// cout << h << ' ' << w << '\n';
int black = h * w + (H - h) * (W - w);
res = res - tot + 2 * black;
}
return min(n * n - res, res);
}
void Hollwo_Pelw() {
cin >> n >> m;
for (int i = 1, x1, y1, x2, y2; i <= m; i++) {
cin >> x1 >> y1 >> x2 >> y2;
a[i] = rect_t(x1, y1, x2, y2);
}
int res = 1e18;
for (int i = 1; i < n; i++)
if (n % i == 0) res = min(res, solve(i));
cout << res;
}
