#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <limits.h>

#define HASH_SIZE 10007

struct HashNode {
    int value;
    struct HashNode* next;
};

struct HashNode* hashTable[HASH_SIZE];

int hash(int value) {
    return abs(value) % HASH_SIZE;
}

void insert(int value) {
    int index = hash(value);
    struct HashNode* node = malloc(sizeof(struct HashNode));
    node->value = value;
    node->next = hashTable[index];
    hashTable[index] = node;
}

int contains(int value) {
    int index = hash(value);
    struct HashNode* current = hashTable[index];
    while (current != NULL) {
        if (current->value == value) {
            return 1;
        }
        current = current->next;
    }
    return 0;
}

int solution(int* nums1, int nums1Size, int* nums2, int nums2Size) {
    // Initialize hash table
    for (int i = 0; i < HASH_SIZE; i++) {
        hashTable[i] = NULL;
    }
    
    // Insert nums1 into hash table
    for (int i = 0; i < nums1Size; i++) {
        insert(nums1[i]);
    }
    
    int minCommon = INT_MAX;
    int found = 0;
    
    // Check nums2 against hash table
    for (int i = 0; i < nums2Size; i++) {
        if (contains(nums2[i])) {
            if (nums2[i] < minCommon) {
                minCommon = nums2[i];
            }
            found = 1;
        }
    }
    
    return found ? minCommon : -1;
}

int parseArray(char* line, int* arr) {
    int size = 0;
    int i = 1; // Skip opening bracket
    int num = 0;
    int negative = 0;
    int hasNum = 0;
    
    while (line[i] != ']' && line[i] != '\0') {
        if (line[i] == '-') {
            negative = 1;
            hasNum = 1;
        } else if (line[i] >= '0' && line[i] <= '9') {
            num = num * 10 + (line[i] - '0');
            hasNum = 1;
        } else if (line[i] == ',' || line[i] == ']') {
            if (hasNum) {
                arr[size++] = negative ? -num : num;
                num = 0;
                negative = 0;
                hasNum = 0;
            }
        }
        i++;
    }
    
    // Handle last number if no trailing comma
    if (hasNum) {
        arr[size++] = negative ? -num : num;
    }
    
    return size;
}

int main() {
    char line1[1000], line2[1000];
    fgets(line1, sizeof(line1), stdin);
    fgets(line2, sizeof(line2), stdin);
    
    int nums1[1000], nums2[1000];
    int nums1Size = parseArray(line1, nums1);
    int nums2Size = parseArray(line2, nums2);
    
    printf("%d\n", solution(nums1, nums1Size, nums2, nums2Size));
    return 0;
}