#include <iostream>
using namespace std;
#include <vector>
 
char nextGreatestLetter(vector<char>& letters, char target) {
    int left = 0, right = letters.size();
 
    while (left < right) {
        int mid = left + (right - left) / 2;
        if (letters[mid] > target)
            right = mid;
        else
            left = mid + 1;
    }
 
    return letters[left % letters.size()];
}
 
int main() {
    vector<char> letters = {'c', 'f', 'j'};
    char target = 'c';
 
    cout << "Next greatest letter: " << nextGreatestLetter(letters, target) << endl;
 
    return 0;
}
 

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