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
#include <bits/stdc++.h>

using namespace std;

#define endl '\n'
#define st first
#define nd second
#define pb push_back
#define sz(x) (int)(x).size()
#define all(x) (x).begin(), (x).end()
#define ll long long
ll mod=1000000007;
int inf=1000000007;
ll infl=1000000000000000007;

const int N=300007;

ll P[N];
ll DP[N];
bool p[N];
map<ll,int>mapa;

ll BIT[N][2];
ll que(int x,bool b) {
	ll s=0;
	for (;x;x-=x&-x) s+=BIT[x][b];
	return s;
}
void ins(int x,ll s,bool b) {
	for (;x<N;x+=x&-x) BIT[x][b]+=s;
}

int main()
{
    ios_base::sync_with_stdio(0);
    cin.tie(0);
    cout.tie(0);
    int n;
    cin>>n;
    set<ll>S;
    S.insert(0);
    for(int i=1;i<=n;i++)
    {
        ll a;
        cin>>a;
        P[i]=(P[i-1]+a)%mod;
        S.insert(P[i]);
        p[i]=P[i]%2;
    }
    int it=0;
    for(auto x:S) mapa[x]=++it;
    for(int i=0;i<=n;i++) P[i]=mapa[P[i]];
    ins(P[0],1,p[0]);
    for(int i=1;i<=n;i++)
    {
        DP[i]=(que(P[i],p[i])+que(N-1,!p[i])-que(P[i],!p[i])+mod)%mod;
        ins(P[i],DP[i],p[i]);
    }
    cout<<DP[n];

    return 0;
}