#include <bits/stdc++.h>
using namespace std;
typedef pair<int, int> pi;
typedef vector<int> vi;
typedef long long ll;
typedef pair<ll, ll> pl;
#define pb push_back
#define mp make_pair
#define f first
#define s second
#define sz(x) (int)(x).size()
void ckmin(ll& a, ll b){
a = min(a, b);
}
void ADD(pl& a, pl b){
a.f+=b.f;
a.s+=b.s;
}
void print(pi a){
cout << a.f << " " << a.s << "\n";
cout.flush();
}
void print(pl a){
cout << "pl: " << a.f << " " << a.s << "\n";
cout.flush();
}
const ll INF = 1e18;
const int mx = 100005;
int N, K;
int X1[mx];
int Y1[mx];
int X2[mx];
int Y2[mx];
pl shouldBe(int X, int Y, int SZ, bool white_corn){
assert(X % SZ == 0 && Y % SZ == 0);
ll squares = ll(X/SZ)*ll(Y/SZ);
ll white_squares = (squares+1)/2;
if(!white_corn){
white_squares = squares-white_squares;
}
ll should_be_white = white_squares*ll(SZ)*ll(SZ);
// cout << "squares: " << squares << "\n";
// cout << "should_be_white: " << should_be_white << "\n";
return mp(should_be_white, ll(X)*ll(Y)-should_be_white);
}
int SZ;
bool shouldBeWhite(const pi& a){
return (a.f/SZ+a.s/SZ + 1) % 2;
}
pl doSingle(pi corner11, pi corner22){
ll area = ll(corner22.s+1-corner11.s)*ll(corner22.f+1-corner11.f);
if(shouldBeWhite(corner11)){
return mp(area, 0);
}
return mp(0, area);
}
pl doEdge(pi corner11, pi corner22){
// cout << corner11.f << " " << corner11.s << " " << corner22.f << " " << corner22.s << "\n";
// cout.flush();
if(corner11.s/SZ == corner22.s/SZ && corner11.f % SZ == 0 && (corner22.f+1) % SZ == 0){
swap(corner11.f, corner11.s);
swap(corner22.f, corner22.s);
}
assert((corner22.s+1) % SZ == 0);
assert(corner11.f/SZ == corner22.f/SZ);
int rect_num = (corner22.s+1-corner11.s)/SZ;
ll rect_area = ll(corner22.f-corner11.f+1)*SZ;
int white_num = (rect_num+1)/2;
int black_num = rect_num-white_num;
if(!shouldBeWhite(corner11)){
swap(white_num, black_num);
}
return mp(rect_area*white_num, rect_area*black_num);
}
pl doBig(pi corner11, pi corner22){
assert(corner11.f % SZ == 0 && corner11.s % SZ == 0);
assert((corner22.f+1) % SZ == 0 && (corner22.s+1) % SZ == 0);
ll rect_num = ll(corner22.f+1-corner11.f)/SZ*ll(corner22.s+1-corner11.s)/SZ;
ll white_num = (rect_num+1)/2;
ll black_num = rect_num-white_num;
if(!shouldBeWhite(corner11)){
swap(white_num, black_num);
}
ll square_area = ll(SZ)*ll(SZ);
return mp(square_area*white_num, square_area*black_num);
}
ll getAns(){ //bottom left should be white, count # of flips
// cout << "SZ = " << SZ << "\n";
// cout.flush();
ll flip_to_white = 0;
ll flip_to_black = 0;
ll area_sum = 0;
for(int i = 1; i <= K; i++){
pi corner11 = mp(X1[i], Y1[i]);
pi corner22 = mp(X2[i], Y2[i]);
area_sum+=ll(corner22.s-corner11.s+1)*ll(corner22.f-corner11.f+1);
pl res = mp(0, 0);
if(corner11.f/SZ < corner22.f/SZ && corner11.s/SZ < corner22.s/SZ){
pi CORNER11 = mp(corner11.f/SZ*SZ+SZ-1, corner11.s/SZ*SZ+SZ-1);
pi CORNER22 = mp(corner22.f/SZ*SZ, corner22.s/SZ*SZ);
// print(corner11);
// print(CORNER11);
// print(CORNER22);
// print(corner22);
ADD(res, doSingle(corner11, CORNER11));
ADD(res, doSingle(CORNER22, corner22));
ADD(res, doSingle(mp(corner11.f, CORNER22.s), mp(CORNER11.f, corner22.s)));
ADD(res, doSingle(mp(CORNER22.f, corner11.s), mp(corner22.f, CORNER11.s)));
// print(res);
ADD(res, doEdge(mp(corner11.f, CORNER11.s+1), mp(CORNER11.f, CORNER22.s-1)));
ADD(res, doEdge(mp(CORNER11.f+1, corner11.s), mp(CORNER22.f-1, CORNER11.s)));
ADD(res, doEdge(mp(CORNER22.f, CORNER11.s+1), mp(corner22.f, CORNER22.s-1)));
ADD(res, doEdge(mp(CORNER11.f+1, CORNER22.s), mp(CORNER22.f-1, corner22.s)));
// print(res);
ADD(res, doBig(mp(CORNER11.f+1, CORNER11.s+1), mp(CORNER22.f-1, CORNER22.s-1)));
// print(res);
}
else if(corner11.f/SZ == corner22.f/SZ && corner11.s/SZ == corner22.s/SZ){
ADD(res, doSingle(corner11, corner22));
}
else{
pi CORNER11 = mp(-1, -1);
pi CORNER22 = mp(-1, -1);
if(corner11.f/SZ == corner22.f/SZ){
CORNER11 = mp(corner22.f, corner11.s/SZ*SZ+SZ-1);
CORNER22 = mp(corner11.f, corner22.s/SZ*SZ);
}
else{
CORNER11 = mp(corner11.f/SZ*SZ+SZ-1, corner22.s);
CORNER22 = mp(corner22.f/SZ*SZ, corner11.s);
}
ADD(res, doSingle(corner11, CORNER11));
// cout << "EDGE" << " " << res.f << " " << res.s << "\n";
ADD(res, doSingle(CORNER22, corner22));
// cout << "EDGE" << " " << res.f << " " << res.s << "\n";
// print(corner11);
// print(CORNER11);
// print(CORNER22);
// print(corner22);
if(corner11.f/SZ == corner22.f/SZ){
ADD(res, doEdge(mp(corner11.f, CORNER11.s+1), mp(corner22.f, CORNER22.s-1)));
// cout << "CASE 1 " << "\n";
}
else{
ADD(res, doEdge(mp(CORNER11.f+1, corner11.s), mp(CORNER22.f-1, corner22.s)));
}
// cout << "EDGE" << " " << res.f << " " << res.s << "\n";
}
// cout << i << " (" << res.f << ", " << res.s << ") \n";
flip_to_white+=res.f;
flip_to_black+=res.s;
}
// assert(area_sum == flip_to_white+flip_to_black);
// cout << "flip_to_white, black: " << flip_to_white << ", " << flip_to_black << "\n";
ll should_be_black = shouldBe(N, N, SZ, 1).s;
return flip_to_white+(should_be_black-flip_to_black);
}
int main(){
cin.tie(0)->sync_with_stdio(0);
cin >> N >> K;
for(int i = 1; i <= K; i++){
cin >> X1[i] >> Y1[i] >> X2[i] >> Y2[i];
X1[i]--; Y1[i]--; X2[i]--; Y2[i]--;
}
ll ans = INF;
for(int i = 1; i < N; i++){
if(N % i == 0){
SZ = i;
ll res = getAns();
// cout << "i, res: " << i << ", " << res << "\n";
ckmin(ans, res);
ckmin(ans, ll(N)*ll(N)-res);
}
}
cout << ans << "\n";
}
