#include<stdio.h>
int main()
{
    int N,M,i,j,temp,cnt,a,b,arr[10000];
    while(scanf("%d",&N)==1)
    {
        for(i=0;i<N;i++)
            scanf("%d",&arr[i]);
        scanf("%d",&M);
        for(i=0;i<N-1;i++)
        {
            cnt=0;
            for(j=0;j<(N-i)-1;j++)
            {
                if(arr[j]>arr[j+1])
                {
                    temp=arr[j];
                    arr[j]=arr[j+1];
                    arr[j+1]=temp;
                    cnt++;
                }
            }
            if(cnt==0)
                break;
        }
        i=0;j=N-1;
        while(i<j){
            if(arr[i]+arr[j]>M)
            {
                j--;
            }
            else if(arr[i]+arr[j]==M)
            {
                a=i;
                b=j;
                i++;
                j--;
            }
            else if(arr[i]+arr[j]<M)
            {
                i++;
            }
        }
        printf("Peter should buy books whose prices are %d and %d.\n",arr[a],arr[b]);
        printf("\n");
    }
    return 0;
}