Code

#include <bits/stdc++.h>

using namespace std;


int main()
{
    int n, x;
    while(scanf("%d", &n)!=EOF)
    {
        vector<int> v;
        for(int i=0 ; i<n ; i++)
        {
            cin >> x;
            v.push_back(x);
        }
        int total;
        cin >> total;
        sort(v.begin(),v.end());
        int mid = n/2;
        int i=0;
        int j=1;
        while(v[mid]+v[i]!=total)
        {
            i++;
            if(i==n)
                {
                    i=0;
                    mid += j;
                }
            if(j+mid==n)
            {
                mid=0;
            }
        }
        if(v[i] <= v[mid])
            printf("Peter should buy books whose prices are %d and %d.\n", v[i], v[mid]);
        else
            printf("Peter should buy books whose prices are %d and %d.\n", v[mid], v[i]);

    }

}