public class Solution {
    public String convertToTitle(int n) {
     return convertToTitle(--n / 26) + (char)('A' + (n % 26));
    }
}

public class Solution {
    public String convertToTitle(int n) {
      StringBuffer sb=new StringBuffer();
      while(n>0){
         --n;
        sb.append((char)(n%26+'A'));
        n/=26;
      }
      return sb.reverse().toString();
    }
}