// author : lox
#pragma GCC optimize("O3")
#pragma GCC target("popcnt")
#include <bits/stdc++.h>
using namespace std;
#define IZhO_SILVER ios_base::sync_with_stdio(0);cin.tie(0);cout.tie(0);
#define popcnt __builtin_popcount
#define all(a) a.begin(),a.end()
#define low_b lower_bound
#define up_b upper_bound
#define vii vector<pair<ll,ll>>
#define vll vector<pair<ll,ll>>
#define pii pair<ll,ll>
#define mii map<ll,ll>
#define pll pair<ll,ll>
#define mll map<ll,ll>
#define vi vector<ll>
#define vl vector<ll>
#define pb push_back
#define endl '\n'
#define Y second
#define X first
typedef long double ld;
typedef long long ll;
const long long dx[4]={1,-1,0,0},dy[4]={0,0,1,-1},col=107,N=1e6+777;
const ll mod=1e9+7,inf=1e18;
void fre_open(){freopen("file.in","r",stdin);freopen("file.out","w",stdout);}
ll binpow(ll n,ll k){if(k<0)return 0ll;if(k==0)return 1ll;if(k%2)return (binpow(n,k-1)*n)%mod;ll kk=binpow(n,k/2)%mod;return (kk*kk)%mod;}
int a[2001][2001];
int n,k;
int pr(int x){
for(int i=1; i*i<=x; ++i) if(x%i==0)return 0;
return 1;
}
void solve(){
cin>>n>>k;
if(k==0){
int x=n*n/2;
for(int i=n/2; i>=1; --i)if(n%i==0)x=min(x,i*i*((n/i)*(n/i)/2));
cout<<x;
return;
}
if(pr(n)){
int x=n*n/2;
int x2=x+1;
for(int c=0, i1,i2,j1,j2;c<k; ++c){
cin>>i1>>j1>>i2>>j2;
for(int i=i1; i<=i2; ++i)
for(int j=j1; j<=j2; ++j)
{
if(i%2==j%2) x++,x2--;
if(i%2!=j%2) x2++,x--;
}
}
cout<<min(x,x2);
return;
}
for(int i=1; i<=k; ++i){
ll x,y,tox,toy;
cin>>x>>y>>tox>>toy;
a[x][y]=1;
}
int ans=mod;
for(int d=1; d*d<=n; ++d){
if(n%d!=0) continue;
int res=0,res2=0;
for(int i=1; i<=n; ++i){
for(int j=1; j<=n; ++j){
int x=(i+(d-1))/d;
int y=(j+(d-1))/d;
if((x+y)%2 && a[i][j]) ++res2;
if((x+y)%2 && !a[i][j]) ++res;
if(!((x+y)%2) && a[i][j]) ++res;
if(!((x+y)%2) && !a[i][j]) ++res2;
}
}
ans=min({ans,res,res2});
//cout<<d<<' '<<res<<' '<<res2<<endl;
int f=n/d;
res=0,res2=0;
for(int i=1; i<=n; ++i){
for(int j=1; j<=n; ++j){
int x=(i+(f-1))/f;
int y=(j+(f-1))/f;
if((x+y)%2 && a[i][j]) ++res2;
if((x+y)%2 && !a[i][j]) ++res;
if(!((x+y)%2) && a[i][j]) ++res;
if(!((x+y)%2) && !a[i][j]) ++res2;
}
}
if(d==1){
ans=min(ans,max(res,res2));
continue;
}
ans=min({ans,res,res2});
//cout<<d<<' '<<res<<' '<<res2<<endl;
}
cout<<ans<<endl;
}
/*
6 8
3 3 3 3
1 2 1 2
3 4 3 4
5 5 5 5
4 3 4 3
4 4 4 4
2 1 2 1
3 6 3 6*/
int main() {
//fre_open();
IZhO_SILVER;
ll tt=1;
//cin>>tt;
while(tt--) solve();
}
