#include <bits/stdc++.h>using namespace std;typedef long long int LL;#define st first
#define nd second
#define pb push_back
#define mp make_pair
#define pll pair <LL, LL>
#define pii pair <int, int>
#define rep(i,x) for(int i=1;i<=x;i++)const int N = 1e5+7;
const int MX = 1e9+7;
const LL INF = 1e18+9LL;int main(){char s[100];scanf("%s",s); int l=strlen(s);if(l%2){cout<<s[l/2];for(int i=l/2-1;i>=0;i--)cout<<s[l-i-1]<<s[i];}else {for(int i=l/2-1;i>=0;i--)cout<<s[i]<<s[l-i-1]; }
}

#include <bits/stdc++.h>using namespace std;typedef long long int LL;#define st first
#define nd second
#define pb push_back
#define mp make_pair
#define pll pair <LL, LL>
#define pii pair <int, int>
#define rep(i,x) for(int i=1;i<=x;i++)const int N = 1e5+7;
const int MX = 1e9+7;
const LL INF = 1e18+9LL;int main(){int n,k;scanf("%d%d",&n,&k);int ans=MX;rep(i,k-1){if(n%i)continue;ans=min(n/i*k+i,ans);}cout<<ans;
}

#include <bits/stdc++.h>using namespace std;typedef long long int LL;#define st first
#define nd second
#define pb push_back
#define mp make_pair
#define pll pair <LL, LL>
#define pii pair <int, int>
#define rep(i,x) for(int i=1;i<=x;i++)const int N = 1e3+7;
const int MX = 1e9+7;
const LL INF = 1e18+9LL;pii a[4];pii ans[N*N];
int cnt;int cmp(pii a,pii b){return a.st<b.st;
}int main(){rep(i,3){int x,y;scanf("%d%d",&x,&y);a[i]=mp(x,y);}sort(a+1,a+4,cmp);for(int i=a[1].st;i<a[2].st;i++)ans[++cnt]=mp(i,a[1].nd);for(int i=a[2].st+1;i<=a[3].st;i++)ans[++cnt]=mp(i,a[3].nd);for(int i=min(min(a[1].nd,a[2].nd),a[3].nd);i<=max(max(a[1].nd,a[2].nd),a[3].nd);i++){ans[++cnt]=mp(a[2].st,i);}cout<<cnt<<endl;rep(i,cnt)cout<<ans[i].st<<" "<<ans[i].nd<<endl;
}

#include <bits/stdc++.h>using namespace std;typedef long long int LL;#define st first
#define nd second
#define pb push_back
#define mp make_pair
#define pll pair <LL, LL>
#define pii pair <int, int>
#define rep(i,x) for(int i=1;i<=x;i++)const int N = 1e5+7;
const int MX = 1e9+7;
const LL INF = 1e18+9LL;vector< int > to[N];int sz[N];void dfs(int x,int f){if(to[x].size()==1)sz[x]=1;for(int i=0;i<to[x].size();i++){if(to[x][i]!=f){dfs(to[x][i],x);sz[x]+=sz[to[x][i]];}}
}int main(){int n;double s;scanf("%d%lf",&n,&s);rep(i,n-1){int u,v;scanf("%d%d",&u,&v);to[u].pb(v);to[v].pb(u);}dfs(1,0);int f=0;for(int i=0;i<to[1].size();i++)if(sz[to[1][i]]==sz[1]){f=1;break;}if(f==1)printf("%.10lf",s/(sz[1]+1)*2);else printf("%.10lf",s/sz[1]*2);
}