#include <bits/stdc++.h>
#define F first
#define S second
#define pb push_back
#define ppb pop_back
#define ep insert
#define endl '\n'
#define elif else if
#define pow pwr
#define sqrt sqrtt
//#define int long long
#define ll long long
#define y1 YONE
typedef unsigned long long ull;
using namespace std;
const int N=2e5+5;
int n,x[N],y[N],m,inp;
int32_t main(){
ios_base::sync_with_stdio(false);cin.tie(NULL);cout.tie(NULL);
cin>>inp>>m;
for (int i=1;i<=inp;i++){
int xx,yy;
cin>>xx>>yy;
if (i<=2){
x[++n]=xx;
y[n]=yy;
continue;
}
if (xx==x[n] && xx==x[n-1]){
x[n]=xx;
y[n]=yy;
continue;
}
if (yy==y[n] && yy==y[n-1]){
x[n]=xx;
y[n]=yy;
continue;
}
x[++n]=xx;
y[n]=yy;
}
if (n==2){
cout<<m<<endl;
return 0;
}
if (n==4){
sort(x+1,x+1+n);
sort(y+1,y+1+n);
if (y[1]==y[n]){
cout<<m<<endl;
return 0;
}
if ((y[n]-y[1])&1){
cout<<x[1]<<endl;
return 0;
}
cout<<x[n]-bool((x[n]-x[1])&1)<<endl;
return 0;
}
if (n==6){
pair<int,int> mn={INT_MAX,INT_MAX};
vector<pair<int,int>> v;
for (int i=1;i<=n;i++) v.pb({x[i],y[i]}),mn=min(mn,v.back());
while (v[0]!=mn){
v.pb(v[0]);
v.erase(v.begin());
}
if (v[1].F!=v[0].F) reverse(v.begin()+1,v.end());
//for (auto u:v) cout<<u.F<<' '<<u.S<<endl;
int ans=v[0].F;
if ((v[1].S-v[0].S)%2==0){
if ((v[2].F-v[0].F)&1){
cout<<v[2].F-1<<endl;
return 0;
}
ans=v[2].F;
}
else{
cout<<ans<<endl;
return 0;
}
if ((v[4].S-v[0].S)%2==0){
ans=v.back().F-bool((v.back().F-v[0].F)&1);
}
cout<<ans<<endl;
return 0;
}
return 0;
}
