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
#include <bits/stdc++.h>
using namespace std;
using ll = long long;
#define FOR(i,a,b) for(ll i=a; i<=b; ++i)
#define pb push_back
#define ssize(v) (ll)(v.size())
#define fi first 
#define se second 

constexpr int MAX_N=5e3+14,ZERO_SUM=1e7+14, MAX_SUM=2e7+28;
ll N, inp[MAX_N], qtSum[MAX_SUM], rres=0;
vector<pair<ll,ll>> sqnc;

void Input(){
    ll cSum;
    cin>>N;
    FOR(i,0,N-1) cin>>inp[i];
    FOR(i,0,N-1){
        cSum=0;
        FOR(j,i,N-1){
            cSum+=inp[j];
            ++qtSum[ZERO_SUM+cSum];
        }
    }
    FOR(i,0,MAX_SUM-1){
        if(qtSum[i]==0)continue;
        sqnc.pb({i-ZERO_SUM,qtSum[i]});
    }
}
void Solve(){
    FOR(i,0,ssize(sqnc)-1){
        if(-(2*sqnc[i].fi)>sqnc[i].fi) rres+=(((qtSum[ZERO_SUM+sqnc[i].fi]-1)*qtSum[ZERO_SUM+sqnc[i].fi])/2)*qtSum[ZERO_SUM-(2*sqnc[i].fi)];
        FOR(j,i+1,ssize(sqnc)-1){
            if(-sqnc[i].fi-sqnc[j].fi<sqnc[j].fi) break;
            if(-sqnc[i].fi-sqnc[j].fi==sqnc[j].fi) {
                rres+=qtSum[ZERO_SUM+sqnc[i].fi]*((qtSum[ZERO_SUM+sqnc[j].fi]*(qtSum[ZERO_SUM+sqnc[j].fi]-1))/2);
                // cout<<"dwa - i:"<<i<<" j:"<<j<<" rres:"<<rres<<"\n";
                continue;
            }
            rres+=qtSum[ZERO_SUM+sqnc[i].fi]*qtSum[ZERO_SUM+sqnc[j].fi]*qtSum[ZERO_SUM-sqnc[i].fi-sqnc[j].fi];
            // cout<<"i:"<<i<<" j:"<<j<<" rres:"<<rres<<"\n";
        }
        // cout<<"i:"<<i<<" rres:"<<rres<<"\n";
    }
    rres+=((qtSum[ZERO_SUM]*(qtSum[ZERO_SUM]-1)*(qtSum[ZERO_SUM]-2))/6);
    cout<<rres<<"\n";

}
int main(){
    ios_base::sync_with_stdio(0);
    cin.tie(0), cout.tie(0);

    Input();
    Solve();

    // cout<<"\nsqnc:\n";
    // for(auto cE:sqnc){
    //     cout<<" "<<cE.fi<<", "<<cE.se<<"\n";
    // }
}