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

int solution(int* nums, int numsSize, int target) {
    int left = 0, right = numsSize;
    
    // Find upper bound (first element > target)
    while (left < right) {
        int mid = (left + right) / 2;
        if (nums[mid] <= target) {
            left = mid + 1;
        } else {
            right = mid;
        }
    }
    
    // Check if target exists at upper_bound - 1
    if (left > 0 && nums[left - 1] == target) {
        return left - 1;
    }
    return -1;
}

int main() {
    char line[1000];
    fgets(line, sizeof(line), stdin);
    
    int nums[1000];
    int numsSize = 0;
    
    // Parse the array manually
    char* p = line;
    // Find the opening bracket
    while (*p && *p != '[') p++;
    if (*p == '[') p++;
    
    // Parse numbers until closing bracket
    while (*p && *p != ']') {
        // Skip whitespace and commas
        while (*p == ' ' || *p == ',') p++;
        if (*p == ']' || *p == '\0') break;
        
        // Parse the number
        char* endptr;
        int num = (int)strtol(p, &endptr, 10);
        if (endptr != p) {  // Successfully parsed a number
            nums[numsSize++] = num;
            p = endptr;
        } else {
            break;
        }
    }
    
    int target;
    scanf("%d", &target);
    
    printf("%d\n", solution(nums, numsSize, target));
    return 0;
}