买帽子——百度2017春招笔试真题编程题（一）

import java.util.Scanner;

public class Main {
public static void main(String[] args) {
Scanner fin=new Scanner(System.in);
int N=fin.nextInt();
int[] num=new int
;
int[] res = new int[1001];
for(int i = 0; i < N; i++){
num[i] = fin.nextInt();
}

for(int i = 0; i < N; i++){
res[num[i]]++;
}
int n = 0;
for(int i = 0; i < 1001; i++){
if(res[i] != 0){
n++;
}
if(n == 3){
System.out.println(i);
return;
}
}
System.out.println(-1);
}
}