import java.util.*;

public class Main {

	public static void main(String[] args) {

		// 入力
		Scanner sc = new Scanner(System.in);
		int x[] = new int[6];
		x[1] = Integer.parseInt(sc.next());
		x[2] = Integer.parseInt(sc.next());
		x[3] = Integer.parseInt(sc.next());
		x[4] = Integer.parseInt(sc.next());
		x[5] = Integer.parseInt(sc.next());

		// 0になっているのを見つける
		for (int i = 1; i <= 5; i++) {
			if (x[i] == 0) {
				System.out.println(i);
			}
		}
	}

}
/tmp/hf-datasets-cache/medium/datasets/42704881117311-config-parquet-and-info-qiankunmu-Project_CodeNet-896c9d36/hub/datasets--qiankunmu--Project_CodeNet_Python800_and_Java250/snapshots/c899fde44a77ba1cc14973ed3de064e4ff3aadc7/Project_CodeNet_Java250.tar.gz