ARC119C

// Problem: C - ARC Wrecker 2
// Contest: AtCoder - AtCoder Regular Contest 119
// URL: https://atcoder.jp/contests/arc119/tasks/arc119_c
// Memory Limit: 1024 MB
// Time Limit: 2000 ms
//
// Powered by CP Editor (https://cpeditor.org)

#include <assert.h>
#include <bits/stdc++.h>
using namespace std;
#define dbg(...) logger(#__VA_ARGS__, __VA_ARGS__)
template <typename... Args> void logger(string vars, Args &&... values)
{
    cerr << vars << " = ";
    string delim = "";
    (..., (cerr << delim << values, delim = ", "));
    cerr << endl;
}

template <class T> inline auto vv(int m) { return vector<vector<T>>(m, vector<T>(m)); }
template <class T> inline auto vv(int m, int n) { return vector<vector<T>>(m, vector<T>(n)); }
template <class T, T init> inline auto vv(int m) { return vector<vector<T>>(m, vector<T>(m, init)); }
template <class T, T init> inline auto vv(int m, int n) { return vector<vector<T>>(m, vector<T>(n, init)); }

template <class T> using mpq = priority_queue<T, vector<T>, greater<T>>;

using ll = long long;
using pii = pair<int, int>;
using vl = vector<ll>;
using vi = vector<int>;

int main(int argc, char **argv)
{
    int n;
    cin >> n;
    vi a(n);
    for (auto &x : a)
        cin >> x;
    unordered_map<ll, int> s;
    s[0] = 1;
    ll flag = 1;
    ll sum = 0;
    ll cnt = 0;
    for (auto x : a)
        sum += flag * x, flag = -1 * flag, cnt += s[sum], s[sum] += 1;
    cout << cnt << endl;
    return 0;
};