//Date: 2025-01-04 14:01:04
#include<bits/stdc++.h>
using namespace std;
#define int long long
#define ldb long double
inline int rd() {
    int s=0,m=0;char ch=getchar();
    while(!isdigit(ch)) {if(ch=='-')m=1;ch=getchar();}
    while( isdigit(ch)) s=(s<<3)+(s<<1)+(ch^48),ch=getchar();
    return m?-s:s;
}
bool MBE;
namespace SOLVER {
int n;ldb p[500005],f[500005],ans;
const double eps=1e-12;
struct Line {ldb k,b;ldb f(int x) {return k*x+b;}};
int cnt;struct Node {int l,r;Line val;};
struct LiChao_Segment_Tree {
  	Node t[4*500005];
	int ls(int p) {return p<<1;}
	int rs(int p) {return p<<1|1;}
	void build(int p,int l,int r) {
		t[p].l=l,t[p].r=r;
		if(l==r) return;
		int m=(l+r)>>1;
		build(ls(p),l,m);build(rs(p),m+1,r);
	}
	int cmp(double a,double b) {return (a-b>eps?1:(b-a>eps?-1:0));}
	void update(int p,Line v) {//区间修改
        Line &u=t[p].val;
        int mid=(t[p].l+t[p].r)>>1,bm=cmp(v.f(mid),u.f(mid));
        if(bm==1) swap(u,v);
        int bl=cmp(v.f(t[p].l),u.f(t[p].l)),br=cmp(v.f(t[p].r),u.f(t[p].r));
        if(bl==1) update(ls(p),v);
        if(br==1) update(rs(p),v);
        return;
	}
	Line query(int p,int x) {
		if(t[p].l==t[p].r) return t[p].val;
		Line s=t[p].val,u;int m=(t[p].l+t[p].r)>>1;
		if(x<=m) u=query(ls(p),x);
		else u=query(rs(p),x);
		if(s.f(x)<u.f(x)) return u;
		return s;
	}
} t;
void MAIN() {
    cin>>n;for(int i=1;i<=n;i++) scanf("%Lf",&p[i]);
    t.build(1,1,n);
    for(int i=n;i>=1;i--) {
        f[i]=p[i]*i;f[i]=max(f[i],t.query(1,i).f(i)*p[i]);ans=max(ans,f[i]);
        t.update(1,Line{1-p[i],f[i]});
    }
    printf("%.20Lf\n",ans);
}
}
bool MED;
signed main() {
    //freopen(".in","r",stdin);freopen(".out","w",stdout);
    for(int tt=1;tt;tt--) SOLVER::MAIN();
    cerr<<(&MBE-&MED)/1024<<" KB, "<<1000*clock()/CLOCKS_PER_SEC<<" ms\n";
    return 0;
}