C++ :

#include<iostream>
#include<vector>
using namespace std;

int main(){
	int a;cin>>a;
	int i,j,k;
	int sum=a;
	vector<int>v;
	for(i=0;i<a;i++){
		int b;cin>>b;
		v.push_back(b);
	}
	sum=a;
	for(i=0;i<v.size();i++){
		k=v[i]%sum;
		for(j=i+1;j<v.size();j++){
			if(v[j]%sum==k){
				sum++;
				i=0;
			}
		}
	}
	cout<<sum<<endl;
	return 0;
}

Java :

import java.util.Arrays;
import java.util.Scanner;

public class Main {

	public static void main(String[] args) {
		Scanner  scanner = new Scanner(System.in);
		int n = scanner.nextInt();
		int[] arr = new int[n];
		int max = -1 ; 
		for(int i = 0 ; i < n ; i++) {
			arr[i] = scanner.nextInt();
			if(max < arr[i]) {
				max = arr[i];
			}
		}
		findMinNumber(arr, max);
		scanner.close();
	}

	private static void findMinNumber(int[] arr, int maxNumber) {
		boolean[] visited = new boolean[maxNumber];
		arrangePosition(arr, visited, arr.length);
	}

	private static void arrangePosition(int[] arr, boolean[] visited, int min) {
		
		for(int i = 0 ; i < arr.length ; i ++) {
			int temp = arr[i] % min;
			if(visited[temp]) {
				Arrays.fill(visited, false);
				arrangePosition(arr, visited, min+1);
				return;
			} else {
				visited[temp] = true;
			}
		}
		
		System.out.println(min);
	}

}