problemOne

//User function Template for C++



class Solution {
public:
    int maximumNumber(int N) {
        string num = to_string(N);
        bool replaced = false;
        for (int i = 0; i < num.length(); i++) {
            if (num[i] == '7' && !replaced) {
                num[i] = '9';
                replaced = true;
            } else if (num[i] == '7' && replaced) {
                break;
            }
        }
        return stoi(num);
    }
};