Exact Sum - UVa 11057

#include <cstdio>
#include <iostream>
#include <algorithm>

using namespace std;

#define ST first
#define ND second
typedef pair<int,int> PII;
#define REP(i,n) for(int i=0;i<(n);i++)

int A[10010];

int main () {
    int n;
    while(scanf("%d",&n) == 1) {
        REP(i,n) scanf("%d",&A[i]);
        int m;
        scanf("%d",&m);
        sort(A,A+n);
        int aux = 1<<30;
        PII sol;
        REP(i,n) {
            bool b = binary_search(A+i+1,A+n,m-A[i]);
            if(b) {
                int pos = lower_bound(A+i+1,A+n,m-A[i])-A;
                if(abs(A[pos] - A[i]) < aux) {
                    aux = A[pos]-A[i];
                    sol.ST = A[i]; sol.ND = A[pos];
                }
            }
        }
        printf("Peter should buy books whose prices are %d and %d.\n\n",sol.ST,sol.ND);
    }
    return 0;
}