public String convertToTitle(int coln) {
    StringBuilder s = new StringBuilder("");
    
    while(coln>0){
        int m = coln % 26; // to have remainder between 0 to 25
        
        if(m==0){
            m = 26; // to print Z
            coln--; // to ensure it gives 0 to 25 remainder in next iteration
        }
        
        s.append((char)(m+64));
        coln /= 26;
    }
    
    return s.reverse().toString();
}