#include <bits/stdc++.h>
using namespace std;
#define int long long int
#define double long double
inline int power(int a, int b) {
int x = 1;
while (b) {
if (b & 1) x *= a;
a *= a;
b >>= 1;
}
return x;
}
const int M = 1000000007;
const int N = 3e5+9;
const int INF = 2e9+1;
const int LINF = 2000000000000000001;
//_ ***************************** START Below *******************************
vector<int> a;
void consistency(int n) {
int s = 0, e=n-1;
while(s<e){
int mid = s+(e-s)/2;
if(a[mid] == a[mid^1]){
s = mid+1;
}
else{
e = mid;
}
}
cout << e << endl;
}
void solve() {
a = {1,1,2,3,3,4,4,8,8};
int n = a.size();
consistency(n) ;
}
int32_t main() {
ios_base::sync_with_stdio(0); cin.tie(0); cout.tie(0);
int t = 1;
while (t--) {
solve();
}
return 0;
}
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