#include<iostream>
    #include<math.h>
    using namespace std;
    int main()
    {
    int n,m,books[10000],min,x,y;
    while(cin>>n)
    {
        x=0,y=0,min=100000;
    for(int i=0;i<n;i++)
        cin>>books[i];
        cin>>m;
    for(int j=0;j<n-1;j++)
    for(int k=j+1;k<n;k++)
        if(books[j]+books[k]==m && abs(books[j]-books[k])<min)
        min=abs(books[j]-books[k]),x=books[j],y=books[k];

            if(x>y)
            swap(x,y);
            cout<<"Peter should buy books whose prices are "<<x<<" and "<<y<<"."<<endl;

    }

    return 0;
    }