PivotLinks

#include <iostream>
#include <bits/stdc++.h>
using namespace std;

#define pb push_back
#define forn(i, n) for (int i = 0; i < n; i++)
#define ll long long
#define endl "\n"

const int N = 2e5 + 5;
void solve()
{
    int n;
    cin>>n;
    ll a[n];
    forn(i,n)
        cin>>a[i];
    ll pref[n];
    ll suff[n];
    pref[0]=0;
    suff[n-1]=0;
    for(int i=1;i<n;i++)
        pref[i]=a[i-1]+pref[i-1];
    for(int i=n-2;i>=0;i--)
        suff[i]=a[i+1]+suff[i+1];

    for(int i=0;i<n;i++)
    {
        if(pref[i]==suff[i])
        {
            cout<<i<<endl;
            return;
        }
    }
}
int main()
{
    ios_base::sync_with_stdio(false);
    cin.tie(NULL);
    cout.tie(NULL);
    solve();
}