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
#include<bits/stdc++.h>
using namespace std;
#define d(a)cout<<#a<<" = "<<a<<"\n";
#define f first
#define s second
#define mp make_pair
#define TURBO ios_base::sync_with_stdio(0);cin.tie(0);cout.tie(0);
#define ll long long
#define M 1000000007
#define MAXN 300300
#define TREESIZE (1<<20)+10
ll pref[MAXN];
ll a[MAXN];
ll b[MAXN];
map<ll,int>id;
int shift=1;
ll tree[MAXN][2];
void update(int p,ll val,int t){
    for (tree[p += shift][t] = val; p > 1; p >>= 1) tree[p>>1][t] = tree[p][t] + tree[p^1][t];
}
ll querry(int l,int r,int t){
    ll ans=0;
    for(l+=shift,r+=shift+1;l<r;l>>=1,r>>=1){
        if(l&1)(ans+=tree[l++][t])%=M;
        if(r&1)(ans+=tree[--r][t])%=M;
    }
    return ans;
}

int main(){
    TURBO;
    int n;
    cin>>n;
    while (shift<=n)shift<<=1;
    for(int i=1;i<=n;i++)cin>>a[i];
    for(int i=1;i<=n;i++)pref[i]=(pref[i-1]+a[i])%M;
    for(int i=0;i<n;i++)b[i]=pref[i+1];
    sort(b,b+n);
    for(int i=0;i<n;i++)id[b[i]]=i+1;
    update(0,1,0);
    ll res=0;
    for(int i=1;i<=n;i++){
        int k=id[pref[i]];
        if(pref[i]%2){//nieparzysta
            res=(querry(0,k,1)+querry(k+1,n,0))%M;
        }
        else{//parzysta
            res=(querry(0,k,0)+querry(k+1,n,1))%M;
        }
        update(k,res,pref[i]%2);
    }
    cout<<res;
}
//4 1000000006 1 5 1000000004