60分分治求调

#include<bits/stdc++.h>
#define int long long
using namespace std;

const int N = 1e5 + 5;

int n, a[N];

int gcd(int x, int y)
{
	if(y == 0) return x;
	else return gcd(y, x % y);
}
int get(int L, int R)
{
	if(L == R) return a[L];
	if(L + 1 == R) return max({a[L], a[R], gcd(a[L], a[R]) * 2});//
	
	int mid = L + R >> 1, l, r;
	int mx = -0x3f3f3f3f, g;
	
	if(mid + 1 <= R) g = gcd(a[mid], a[mid + 1]);
	l = mid, r = mid + 1;
	while(r < R && !(a[r + 1] % g))
		r ++ ;
	while(l > L && !(a[l - 1] % g))
		l -- ;
	mx = max(mx, g * (r - l + 1));
	
	if(mid - 1 >= L) 
		g = gcd(a[mid], a[mid - 1]);
	l = mid - 1, r = mid;
	while(r < R && !(a[r + 1] % g))
		r ++ ;
	while(l > L && !(a[l - 1] % g))
		l -- ;
	mx = max(mx, g * (r - l + 1));
	
	return max({mx, get(L, mid), get(mid + 1, R)});
}
signed main()
{
	cin >> n;
	for(int i = 1; i <= n; i ++ ) cin >> a[i];
	cout << get(1, n);
	return 0;
}