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#include <vector>
#include <iostream>
#include <sstream>
#include <math.h>
#include <sys/time.h>
#include <cstdlib>
#include <algorithm>
#include <cassert>
#include <cstring>
#include <fstream>
#include <set>
#include <map>
#include <iomanip>
#include <queue>

#define FOR(i,a,b)  for(__typeof(b) i=(a);i<(b);++i)
#define REP(i,a)    FOR(i,0,a)
#define FOREACH(x,c)   for(__typeof(c.begin()) x=c.begin();x != c.end(); x++)
#define ALL(c)      c.begin(),c.end()
#define CLEAR(c)    memset(c,0,sizeof(c))
#define SIZE(c) (int) ((c).size())

#define PB          push_back
#define MP          make_pair
#define X           first
#define Y           second

#define ULL         unsigned long long
#define LL          long long
#define LD          long double
#define II         pair<int, int>
#define DD         pair<double, double>
#define FF          pair<float,float>

#define VC	    vector
#define VI          VC<int>
#define VVI         VC<VI>
#define VVVI        VC<VVI>
#define VD          VC<double>
#define VS          VC<string>
#define VII         VC<II>
#define VDD         VC<DD>
#define VFF         VC<FF>
#define VVD         VC<VD>
#define VVVD        VC<VVD>
#define VULL         VC<ULL>
#define VLL VC<LL>

#define DB(a)       cerr << #a << ": " << a << endl;

using namespace std;

template<class T> void print(VC < T > v) {cerr << "[";if (SIZE(v) != 0) cerr << v[0]; FOR(i, 1, SIZE(v)) cerr << "," << v[i]; cerr << "]\n";}
template<class T> string i2s(T &x) { ostringstream o; o << x; return o.str(); }
VS split(string &s, char c = ' ') {VS all; int p = 0, np; while (np = s.find(c, p), np >= 0) {all.PB(s.substr(p, np - p)); p = np + 1;} if (p < SIZE(s)) all.PB(s.substr(p)); return all;}

//#define MOD 11
#define MOD 1000000007
#define INV2 (MOD/2+1)

struct ITree{
    VLL T;
    int N;
    ITree(int n){
        N = 1;
        while (N < n) N *= 2;
        T = VLL(2*N,0);
    }

    void add(int ind, LL val){
        int i = ind+N;
        T[i] = (T[i]+val)%MOD;
        while (i != 1){
            i = i/2;
            T[i] = (T[2*i] + T[2*i+1])%MOD;
        }
    }

    LL prefix(int R){
        int i = R+N;
        LL s = T[i];
        while (i != 1){
            if (i%2 == 1)
                s = (s+T[i-1])%MOD;
            i = i/2;
        }
        return s;
    }

    LL sum(int L, int R){
        if (L == 0)
            return prefix(R);
        else
            return (MOD+prefix(R)-prefix(L-1))%MOD;
    }
};

int main(int argc, char *argv[]){
    int n;
    cin >> n;
    VLL T(n);
    REP(i,n) cin >> T[i];
    REP(i,n) T[i] = (T[i] * INV2) % MOD;
    // [0,MOD/2] are now even
    
    // S[i] <- sum of elemems with inds <= i
    VLL S(n);
    LL s = 0;
    REP(i,n){
        s = (s+T[i])%MOD;
        S[i] = s;
    }

    // I is a sorted index of all non-empty prefix values
    VLL I(S);
    sort(ALL(I));

    set<LL> tmp(ALL(I));
    I.assign(ALL(tmp));

    ITree IT(SIZE(I));
    
    I.PB(MOD); // sentinel

    LL cnt;
    REP(i,n){
        cnt = (S[i] <= MOD/2);
        // TODO: identify the range of interesting values of prefix (could be reverse range)
        // S[i]-s must be in range [0,MOD/2], so
        // s is in range S[i]-MOD/2,...,S[i] inclusive
        LL L = (S[i]+MOD-MOD/2)%MOD;
        LL R = S[i];
        if (L < R){
            int Lind = lower_bound(ALL(I),L)-I.begin();
            int Rind = upper_bound(ALL(I),R)-I.begin()-1;
            cnt = (cnt + IT.sum(Lind,Rind)) % MOD;
        } else{
            int Lind = lower_bound(ALL(I),L)-I.begin()-1;
            int Rind = upper_bound(ALL(I),R)-I.begin();
            cnt = (cnt + MOD + IT.sum(0,SIZE(I)-2) - IT.sum(Rind,Lind)) % MOD;
        }

        int ind = lower_bound(ALL(I),S[i])-I.begin();
        IT.add(ind,cnt);
    }

    cout << cnt << endl;

    return 0;
}