1
  2
  3
  4
  5
  6
  7
  8
  9
 10
 11
 12
 13
 14
 15
 16
 17
 18
 19
 20
 21
 22
 23
 24
 25
 26
 27
 28
 29
 30
 31
 32
 33
 34
 35
 36
 37
 38
 39
 40
 41
 42
 43
 44
 45
 46
 47
 48
 49
 50
 51
 52
 53
 54
 55
 56
 57
 58
 59
 60
 61
 62
 63
 64
 65
 66
 67
 68
 69
 70
 71
 72
 73
 74
 75
 76
 77
 78
 79
 80
 81
 82
 83
 84
 85
 86
 87
 88
 89
 90
 91
 92
 93
 94
 95
 96
 97
 98
 99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
// clang-format off
#pragma GCC optimize("O3,unroll-loops")
// #pragma GCC target("avx2,bmi,bmi2,lzcnt,popcnt")
#include <bits/stdc++.h>
// #include <ext/pb_ds/assoc_container.hpp>
// #include <ext/pb_ds/tree_policy.hpp>
using namespace std;
template<class Fun>
class y_combinator_result {
    Fun fun_;
public:
    template<class T> explicit y_combinator_result(T &&fun): fun_(forward<T>(fun)) {}
    template<class ...Args> decltype(auto) operator()(Args &&...args) { return fun_(ref(*this), forward<Args>(args)...); }
};
template<class Fun> decltype(auto) y_combinator(Fun &&fun) { return y_combinator_result<decay_t<Fun>>(forward<Fun>(fun)); }
// using namespace __gnu_pbds;
// template <typename T> using ordered_set = tree<T, null_type, less<T>, rb_tree_tag, tree_order_statistics_node_update>;
#define sim template < class c
#define ris return * this
#define dor > debug & operator <<
#define eni(x) sim > typename enable_if<sizeof dud<c>(0) x 1, debug&>::type operator<<(c i) {
sim > struct rge { c b, e; };
sim > rge<c> range(c i, c j) { return rge<c>{i, j}; }
sim > auto dud(c* x) -> decltype(cerr << *x, 0);
sim > char dud(...);
struct debug {
#ifdef XOX
~debug() { cerr << endl; }
eni(!=) cerr << boolalpha << i; ris; }
eni(==) ris << range(begin(i), end(i)); }
sim, class b dor(pair < b, c > d) { ris << "(" << d.first << ", " << d.second << ")"; }
sim dor(rge<c> d) { *this << "["; for (auto it = d.b; it != d.e; ++it) *this << ", " + 2 * (it == d.b) << *it; ris << "]"; }
#else
sim dor(const c&) { ris; }
#endif
};
#define imie(...) " [" << #__VA_ARGS__ ": " << (__VA_ARGS__) << "] "
struct { template <class T> operator T() { T x; cin >> x; return x; } } in;
#define endl '\n'
#define pb emplace_back
#define all(x) begin(x), end(x)
#define sz(x) (int)(x).size()
using i64 = long long;
template <class T> using vt = vector<T>;
template <class T, size_t n> using ar = array<T, n>;
// #define int long long
// clang-format on

struct vtt {
    // [-x, x]
    int x;
    vt<int> v;
    vtt(int x_) : x(x_), v(2 * x_ + 1) {}
    int &operator[](int i) { return v[i + x]; }
    int operator[](int i) const { return v[i + x]; }
};

void solve() {
    int n = in;
    vt<int> ar(n + 1);
    for (int i = 1; i <= n; i++) {
        ar[i] = in;
        ar[i] += ar[i - 1];
    }
    auto daj = [&](int l, int r) { return ar[r] - ar[l - 1]; };
    const int mxa = 20'000;
    vt<vt<int>> pytki(n + 1);
    i64 ans = 0;
    vtt sumy(3 * n * mxa), sumykwadrat(2 * n * mxa);
    for (int i = 1; i <= n; i++) {
        sumy[ar[i]]++;
    }
    for (int i = 1; i <= n; i++) {
        for (int j = i; j <= n; j++) {
            sumykwadrat[daj(i, j)]++;
        }
    }
    for (int i = 1; i <= n; i++) {
        for (int j = 1; j <= n; j++) {
            for (int k = j; k <= n; k++) {
                int need = -(daj(j, k) - ar[i - 1]);
                pytki[i].push_back(need);
                {
                    // odejmij case gdy [j, k] == drugi
                    int need_sec = -(2 * daj(j, k) - ar[i - 1]);
                    ans -= sumy[need_sec];
                }
                {
                    // odejmij case gdy [j, k] j == i
                    if (i == j) {
                        int need_sec = -(2 * daj(j, k));
                        ans -= sumykwadrat[need_sec];
                    }
                }
                {
                    // odejmij case gdy [i, ?] == drugi
                    int need_sec = -(daj(j, k));
                    if (need_sec % 2 == 0) {
                        need_sec /= 2;
                        need_sec = ar[i - 1] + need_sec;
                        ans -= sumy[need_sec];
                    }
                }
                {
                    // co z case gdy wszystko jest rowne?
                    // chyba odjelismy go trzy razy
                    if (i == j && 3 * daj(j, k) == 0) {
                        ans += 2;
                    }
                }
            }
        }
        sumy[ar[i]]--;
    }
    debug() << imie(ans);
    for (int i = n; i >= 1; i--) {
        for (int a = 1; a <= n; a++) {
            for (int b = a; b <= n; b++) {
                sumy[daj(a, b) + ar[i]]++;
            }
        }
        for (auto x : pytki[i]) {
            ans += sumy[x];
        }
    }
    cout << ans / 6 << endl;
}

int32_t main() {
    cin.tie(0)->sync_with_stdio(0);
    int t = 1;
    // int t = in;
    while (t--) {
        solve();
    }
}