#include<stdio.h>
int main()
{
    int a[]={1,2,3,4,5,6,7,8,9,10};
    int b[9],i;
    for(i=0;i<9;i++){
        scanf("%*s%d",b[i]);
    }
    i=0;
    while(1){
        if(a[i]!=b[i]){
            break;
        }
        i++;
    }
    printf("%d\n",a[i]);
    return 0;
}