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

int* parseArray(const char* s, int* size) {
    *size = 0;
    if (strlen(s) <= 2) return NULL;
    
    // Count elements
    for (int i = 1; i < strlen(s) - 1; i++) {
        if (s[i] == ',' || (i == 1)) (*size)++;
    }
    
    int* arr = (int*)malloc(*size * sizeof(int));
    char* str = (char*)malloc(strlen(s));
    strcpy(str, s + 1);
    str[strlen(str) - 1] = '\0';
    
    char* token = strtok(str, ",");
    int i = 0;
    while (token != NULL && i < *size) {
        arr[i++] = atoi(token);
        token = strtok(NULL, ",");
    }
    
    free(str);
    return arr;
}

int arraysEqual(int* arr1, int* arr2, int size) {
    int count1[20001] = {0}; // Range adjustment for negative numbers
    int count2[20001] = {0};
    
    for (int i = 0; i < size; i++) {
        count1[arr1[i] + 10000]++; // Offset for negative numbers
        count2[arr2[i] + 10000]++;
    }
    
    for (int i = 0; i < 20001; i++) {
        if (count1[i] != count2[i]) return 0;
    }
    return 1;
}

int solution(int* nums1, int* nums2, int size) {
    // Try the difference from first pair
    int x = nums2[0] - nums1[0];
    
    int* modifiedNums1 = (int*)malloc(size * sizeof(int));
    for (int i = 0; i < size; i++) {
        modifiedNums1[i] = nums1[i] + x;
    }
    
    int result = x;
    if (!arraysEqual(modifiedNums1, nums2, size)) {
        result = 0;
    }
    
    free(modifiedNums1);
    return result;
}

int main() {
    char line1[1000], line2[1000];
    fgets(line1, sizeof(line1), stdin);
    fgets(line2, sizeof(line2), stdin);
    
    line1[strcspn(line1, "\n")] = 0;
    line2[strcspn(line2, "\n")] = 0;
    
    int size1, size2;
    int* nums1 = parseArray(line1, &size1);
    int* nums2 = parseArray(line2, &size2);
    
    int result = solution(nums1, nums2, size1);
    printf("%d\n", result);
    
    free(nums1);
    free(nums2);
    return 0;
}