#include <bits/stdc++.h>
using namespace std;
int findPartition(const vector<int>& nums){
    int n = nums.size();
    if(n<2) return -1;
    long long total=0; for(int v:nums) total+=v;
    long long left=0; long long bestDiff=LLONG_MAX; int bestIdx=-1;
    for(int i=0;i<n-1;++i){
        left+=nums[i];
        long long right=total-left;
        long long diff= llabs(left-right);
        if(diff<bestDiff){bestDiff=diff; bestIdx=i;}
    }
    return bestIdx;
}
int main(){ios::sync_with_stdio(false);cin.tie(nullptr);
    int n; if(!(cin>>n)) return 0; vector<int> nums(n); for(int i=0;i<n;++i)cin>>nums[i];
    cout<<findPartition(nums);
    return 0;}

import java.io.*;
import java.util.*;
public class Main {
    public static int findPartition(int[] nums){
        int n = nums.length;
        if(n<2) return -1;
        long total=0;
        for(int v:nums) total+=v;
        long left=0;
        long bestDiff=Long.MAX_VALUE;
        int bestIdx=-1;
        for(int i=0;i<n-1;i++){
            left+=nums[i];
            long right=total-left;
            long diff=Math.abs(left-right);
            if(diff<bestDiff){
                bestDiff=diff;
                bestIdx=i;
            }
        }
        return bestIdx;
    }
    public static void main(String[] args) throws Exception {
        BufferedReader br = new BufferedReader(new InputStreamReader(System.in));
        StringTokenizer st = new StringTokenizer(br.readLine());
        int n = Integer.parseInt(st.nextToken());
        int[] nums = new int[n];
        int idx=0;
        while(idx<n){
            if(!st.hasMoreTokens()) st = new StringTokenizer(br.readLine());
            nums[idx++] = Integer.parseInt(st.nextToken());
        }
        System.out.print(findPartition(nums));
    }
}

import sys

def find_partition(nums):
    n = len(nums)
    if n < 2:
        return -1
    total = sum(nums)
    left = 0
    best_diff = None
    best_idx = -1
    for i in range(n-1):
        left += nums[i]
        right = total - left
        diff = abs(left - right)
        if best_diff is None or diff < best_diff:
            best_diff = diff
            best_idx = i
    return best_idx

if __name__ == "__main__":
    data = sys.stdin.read().strip().split()
    if not data:
        sys.exit(0)
    n = int(data[0])
    nums = list(map(int, data[1:1+n]))
    print(find_partition(nums))

function findPartition(nums){
    const n = nums.length;
    if(n<2) return -1;
    let total = 0n;
    for(const v of nums) total += BigInt(v);
    let left = 0n;
    let bestDiff = null;
    let bestIdx = -1;
    for(let i=0;i<n-1;i++){
        left += BigInt(nums[i]);
        const right = total - left;
        const diff = left>right ? left-right : right-left;
        if(bestDiff===null || diff < bestDiff){
            bestDiff = diff;
            bestIdx = i;
        }
    }
    return bestIdx;
}
const fs = require('fs');
const data = fs.readFileSync(0,'utf8').trim().split(/\s+/).map(Number);
if(data.length){
    const n = data[0];
    const nums = data.slice(1,1+n);
    console.log(findPartition(nums).toString());
}