双指针算法，定义层数跟该层第一个数
#include <iostream>
#include <cstring>
#include <cstdio>
#include <algorithm>
using namespace std;
typedef long long LL;
const int N = 1e5 + 10;

int n;
int a[N];

int main(){
    scanf("%d",&n);
    for(int i = 1;i <= n;++i)    scanf("%d",&a[i]);
    int depth = 0;
    LL maxn = -1e9;
    for(int i = 1,d = 1;i <= n;i *= 2,++d){
        LL s = 0;
        for(int j = i;j <= n && j < i + (1 << d - 1);++j)   s += a[j];
        if(maxn <= s){
            maxn = s;
            depth = d;
        }
    }
    printf("%d\n",depth);
    return 0;
}