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

char nextGreatestLetter(char* letters, int lettersSize, char target) {
    int left = 0, right = lettersSize - 1;
    
    // If target is greater than or equal to the last character,
    // or smaller than the first character, wrap around
    if (target >= letters[lettersSize - 1] || target < letters[0]) {
        return letters[0];
    }
    
    // Binary search for the smallest character greater than target
    while (left <= right) {
        int mid = left + (right - left) / 2;
        
        if (letters[mid] > target) {
            // This could be our answer, but check if there's a smaller one
            if (mid == 0 || letters[mid - 1] <= target) {
                return letters[mid];
            }
            right = mid - 1;
        } else {
            left = mid + 1;
        }
    }
    
    return letters[0];  // This shouldn't be reached given our initial check
}

int main() {
    char letters[] = {'c', 'f', 'j'};
    char target = 'd';
    int size = 3;
    printf("%c\n", nextGreatestLetter(letters, size, target));
    return 0;
}