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#include<cstdio>
#include<cstring>
#include<algorithm>
#include<iostream>
#include<queue>
#include<map>
#include<stack>
#include<cmath>
#include<set>
#include<bitset>
#define inc(i,l,r) for(int i=l;i<=r;i++)
#define dec(i,l,r) for(int i=l;i>=r;i--)
#define link(x) for(edge *j=h[x];j;j=j->next)
#define mem(a) memset(a,0,sizeof(a))
#define ll long long
#define eps 1e-8
#define succ(x) (1<<x)
#define lowbit(x) (x&(-x))
#define sqr(x) ((x)*(x))
#define mid (x+y>>1)
#define NM 1048576
#define nm 1024
#define pi 3.1415926535897931
using namespace std;
const ll inf=998244353;
ll read(){
ll x=0,f=1;char ch=getchar();
while(!isdigit(ch)){if(ch=='-')f=-1;ch=getchar();}
while(isdigit(ch))x=x*10+ch-'0',ch=getchar();
return f*x;
}
int n,m;
double a[NM],ans;
void fmt(double*a){
for(int i=0;succ(i)<n;i++)
inc(j,0,n-1)if(j>>i&1)
a[j]=a[j]+a[j^1<<i];
}
int main(){
m=read();
n=succ(m);
inc(i,0,n-1)scanf("%lf",a+i);
fmt(a);
inc(i,0,n-2){
if(fabs(a[i]-1)<eps)return 0*printf("INF\n");
if((m-__builtin_popcount(i)+1)&1)ans-=1/(1-a[i]);
else ans+=1/(1-a[i]);
}
return 0*printf("%.7lf\n",ans);
}
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