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

#define ll long long

int main()
{
    ios_base::sync_with_stdio(false);
    cin.tie(NULL);

#ifndef ONLINE_JUDGE
    freopen("split_in.txt", "r", stdin);
#endif

    int n;
    cin >> n;

    ll arr[n] = {};
    cin >> arr[0];

    ll zeros = 0;
    if (arr[0] == 0)
        zeros = 1;

    for (int i = 1; i < n; ++i)
    {
        ll k;
        cin >> k;

        arr[i] = arr[i - 1] + k;

        if (arr[i] == 0)
            ++zeros;
    }

    if (arr[n - 1] % 3 != 0 || n < 3)
    {
        cout << 0;
        return 0;
    }

    if (arr[n - 1] == 0)
    {
        zeros -= 2;
        cout << zeros * (zeros + 1) / 2;
        return 0;
    }

    ll size = arr[n - 1] / 3;

    ll count1[n] = {}, temp[n + 1] = {};
    int index1 = 0, index2 = 0;

    for (int i = 0; i < n; ++i)
    {
        if (arr[i] == size)
        {
            if (temp[index1] == 0)
                ++count1[index1];
            else
                ++count1[++index1];
        }
        else if (arr[i] == 2 * size)
        {
            if (count1[index2 + 1] == 0)
            {
                if (count1[index2] > 0)
                    ++temp[index2];
            }
            else
                ++temp[++index2];
        }
    }

    int count2[index2 + 1] = {};

    for (int i = 0; i < index2 + 1; ++i)
        count2[i] = temp[index2 - i] + temp[index2 - i + 1];

    ll sum = 0;

    for (int i = 0; i < index2 + 1; ++i)
        sum += count1[i] * count2[index2 - i];

    cout << sum;

    return 0;
}