Twenty-six hexadecimal

```
public int titleToNumber(String s) {
int sum = 0;
for(int i = s.length()-1; i >= 0; i-- ){
//convert character into a corresponding number.
int temp = (int)(s.charAt(i) - 'A')+1;
sum += temp * Math.pow(26,s.length()-1-i);
}
return sum;
}
```