201612-1 中间数

#include <iostream>
#include <algorithm>
using namespace std;
int main(){
	int n;
	cin>>n;
	int *a=new int[n];
	for(int i=0;i<n;i++){
		cin>>a[i];
	}
	sort(a,a+n);
	int midcount=n/2;
	int num1=0,num2=0;
	for(int i=midcount-1;i>=0;i--){
		if(a[i]==a[midcount]) ;
		else num1++;
	}
	for(int i=midcount+1;i<n;i++){
		if(a[i]==a[midcount]) ;
		else num2++;
	}
	if(num1==num2){
		cout<<a[midcount];
	}
	else cout<<"-1";
	return 0;
}