#include<stdio.h>
#include<string.h>
int main(void){
	char a[100],b[100];
	char x[10],y[10];
	char ap[100000],bp[100000];
	int a1,b1,i;
	scanf("%s%s%s",a,ap,x);
	scanf("%s%s%s",b,bp,y);
	
	a1 = strlen(ap);b1 = strlen(bp);
	
	if(a1 == b1){
		for(i=0;i<a1;i++){
			if(ap[i] > bp[i]){
				printf("%s\n",a); break;
			}else if(ap[i] < bp[i]){
				printf("%s\n",b); break;
			}else if(i == a1-1){
				printf("-1\n"); break;
			}
		}
	}else if(a1 > b1){
		printf("%s\n",a);
	}else if(b1 > a1){
		printf("%s\n",b);
	}
	return 0;
}