// poj1090

#include<algorithm>

#include<iostream>

#include<cstring>

#include<cstdlib>

#include<cstdio>

#include<cmath>

#include<set>

#define MOD 1000000007

#define inf 2147483640

#define LL long long

#define free(a) freopen(a".in","r",stdin);freopen(a".out","w",stdout);

using namespace std;

inline LL getint() {

    LL x=0,f=1;char ch=getchar();

    while (ch>'9' || ch<'0') {if (ch=='-') f=-1;ch=getchar();}

    while (ch>='0' && ch<='9') {x=x*10+ch-'0';ch=getchar();}

    return x*f;

}

int n,a[2000],f[1010][400],t[400];

int main() {

    scanf("%d",&n);

    int sum=0;

    for (int i=1;i<=n;i++) {

        scanf("%d",&a[i]);

        sum+=a[i];

    }

    for (int i=1;i<=n;i++) {

        sum-=a[i];

        if (sum&1) a[i]=!a[i];

    }

    f[1][1]=1;

    for (int i=2;i<=1000;i++) {

        for (int j=1;j<=399;j++) f[i][j]=f[i-1][j]*2;

        for (int j=1;j<=399;j++) {

            f[i][j]+=f[i][j-1]/10;

            f[i][j-1]%=10;

        }

    }

    for (int i=1;i<=n;i++)

        if (a[i]) {

            for (int j=1;j<=399;j++) t[j]+=f[i][j];

            for (int j=1;j<=399;j++) {

                t[j]+=t[j-1]/10;

                t[j-1]%=10;

            }

        }

    int i;

    for (i=399;i>=1;i--) if (t[i]) break;

    if (i==0) printf("0");

    else for (;i>=1;i--) printf("%d",t[i]);

    return 0;

}