#include<stdio.h>


int main(void){
	int i,A[9]={1,2,3,4,5,6,7,8,9},s[9];

	for(i=0;i<9;i++){
		scanf("%d",&s[i]);
	}

	for(i=0;i<9;i++){
		if(s[i]!=A[i]){
			printf("%d",A[i]);
			break;
		}else if(s[9]==A[9])	printf("10");
			
	}

return 0;

}