#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <stdbool.h>
#include <math.h>
int main(void)
{
    char name1[200]="",name2[200]="",point1[10001]="",point2[10001]="",a;
    scanf("%s %s %c\n",&name1,&point1,&a);
    scanf("%s %s %c",&name2,&point2,&a);
    int diflen=strlen(point1)-strlen(point2);
    if(diflen==0)
    {
        diflen=strcmp(point1,point2);
    }
    if(diflen==0)
    {
        printf("-1");
    }
    else if (diflen>0)
    {
        printf("%s",name1);
    }
    else
    {
        printf("%s",name2);
    }
    
    
}