import java.util.Scanner;
public class OneToTen {

	public static void main(String[] args) {
		// TODO 自動生成されたメソッド・スタブ
		int a[]={0,0,0,0,0,0,0,0,0,0};
		int count[]={0,0,0,0,0,0,0,0,0,0};
		Scanner kb=new Scanner(System.in);
		for(int i=0;i<9;i++){
			a[i]=kb.nextInt();
		}

		for(int i=0;i<10;i++){
			switch(a[i]){			
			case 1:count[0]++;
			continue;
			case 2:count[1]++;continue;
			case 3:count[2]++;continue;
			case 4:count[3]++;continue;
			case 5:count[4]++;continue;
			case 6:count[5]++;continue;
			case 7:count[6]++;continue;
			case 8:count[7]++;continue;
			case 9:count[8]++;continue;
			case 10:count[9]++;continue;
			default:continue;
			}

		}
		for(int i=0;i<10;i++){
			if(count[i]==0){
				System.out.printf("%d\n",i+1);
			}
		}
		kb.close();
	}

}