#include <bits/stdc++.h>
using namespace std;
typedef long long ll;
typedef pair<int, int> pii;
typedef pair<ll, ll> pll;
#define ent "\n"
const int maxn = 1e6 + 100;
const ll INF = (ll)1e18 + 100;
const int inf = 1e9 + 100;
const int MOD = 1e9 + 123;
const int maxl = 26;
const int P = 31;
int n, m;
int a[maxn];
int b[maxn];
void test(){
cin >> n >> m;
for(int i = 1; i <= n; i++){
cin >> a[i] >> b[i];
}
vector<int> v;
for(int i = 2; i <= n; i++){
while(v.size() > 1){
int k = v[v.size()-2], j = v.back();
if(a[k] == a[j] && a[j] == a[i]) v.pop_back();
else if(b[k] == b[j] && b[j] == b[i]) v.pop_back();
else break;
} v.push_back(i);
}
int ans = 0;
for(int i: v){
if((b[i] & 1 )|| !b[i]) break;
ans = a[i] - (a[i] & 1);
if(a[i] & 1) break;
}
cout << ans;
}
int main(){
ios_base::sync_with_stdio(0);
cin.tie(0); cout.tie(0);
int t; t = 1;
while(t--) test();
cout << ent;
}
