#include<bits/stdc++.h>
using namespace std;

typedef long double db;

const db eps=1e-8;
const int maxn=1e5+5;

int n; db c;

db p[maxn], q[maxn], p2[maxn];

db check(db s) {
    db res=0;
    for(int i=1;i<=n;i++) res+= p[i]*(1+(1-q[i])*c*s)/(1-(1-q[i])*(1-c));
    return res;    
}

int main() {
    ios::sync_with_stdio(false);
    cin.tie(0), cout.tie(0);
    cin>>n>>c;
    c/=100;
    db sum=0, t;
    for(int i=1;i<=n;i++) cin>>p[i], sum+=p[i];
    for(int i=1;i<=n;i++) p[i]/=sum, p2[i]=sqrt(p[i]);
    if(c==1) {
        db mn=1e9;
        for(int i=1;i<=n;i++) mn=min(mn,p[i]);
        cout<<fixed<<setprecision(10)<<(db)1/mn<<'\n';
        return 0;
    }
    sum=0;
    for(int i=1;i<=n;i++) sum+=p2[i];
    t=(1+(n-1)*c)/sum;
    db lt=0, rt=t;
    while(rt-lt>eps) {
        db mid=(lt+rt)*0.5, res=0;
        for(int i=1;i<=n;i++) res+= q[i]=max((db)0,(p2[i]*mid-c)/(1-c));
        if(res<=1) lt=mid;
        else rt=mid;
    }
    t=lt;
    for(int i=1;i<=n;i++) q[i]=max((db)0,(p2[i]*t-c)/(1-c));
    db l=0, r=1e9;
    while(r-l>eps) {
        db mid=(l+r)*0.5;
        db res=check(mid);
        if(check(mid)<=mid) r=mid;
        else l=mid;
    }
    cout<<fixed<<setprecision(10)<<l<<'\n';
    return 0;
}