#include<iostream>#include<string.h>using namespace std;int ko[1000];int cun[1000][350];int ans[1000];int main(){int length,i,j,sum;cin>>length;sum=0;for(i=0;i<length;i++){cin>>ko[i];sum=sum+ko[i];}for(i=0;i<length;i++){sum=sum-ko[i];if(sum%2==1)ko[i]=1-ko[i];}memset(cun,0,sizeof(cun));cun[0][0]=1;for(i=1;i<length;i++){for(j=0;j<=349;j++){cun[i][j]=cun[i-1][j]*2;}for(j=0;j<=349;j++){if(cun[i][j]>10){cun[i][j+1]=cun[i][j+1]+cun[i][j]/10;cun[i][j]=cun[i][j]%10;}}}memset(ans,0,sizeof(ans));for(i=0;i<length;i++){if(ko[i]==0)continue;int carry=0;for(j=0;j<=349;j++){ans[j]=ans[j]+cun[i][j]+carry;carry=ans[j]/10;ans[j]=ans[j]%10;}}int flag=-1;for(i=400;i>=0;i--)if(ans[i]!=0){flag=i;break;}if(flag==-1)cout<<0;for(i=flag;i>=0;i--)cout<<ans[i];cout<<endl;return 0;}
