LeetCode 1323. Maximum 69 Number

class Solution {
public:
    int maximum69Number (int num) {
        
        string s=to_string(num);
        int l=s.size();
        for(int i=0;i<l;i++)
        {
            if(s[i]=='6')
            {
                s[i]='9';
                break;
            }
        }
        
        int n=stoi(s);
        return n;
        
    }
};