#include<cstdio>
#define repi(i,a,b) for(int i=(a);i<(b);++i)
#define rep(i,a) repi(i,0,a)

const int MAX_M = 10;

int M, S[MAX_M];
double dp[MAX_M+1][1<<MAX_M];

double calc( int a, int b )
{ return S[a]*S[a]/double(S[a]*S[a]+S[b]*S[b]); }

int main()
{
	scanf( "%d", &M );
	rep( i, 1<<M )
		scanf( "%d", S+i );

	rep( j, 1<<M )
		dp[0][j] = 1.0;
	rep( i, M ) rep( j, 1<<M )
	{
		int lb = j/(1<<i+1)*(1<<i+1),
			ub = lb+(1<<i+1),
			mid = lb+ub>>1;

		repi( k, j<mid?mid:lb, j<mid?ub:mid )
			dp[i+1][j] += dp[i][j]*dp[i][k]*calc( j, k );
	}

	printf( "%.7f\n", dp[M][0] );

	return 0;
}