Given a string columnTitle that represents the column title as appear in an Excel sheet, return its corresponding column number. For example: A -> 1 B -> 2 C -> 3 ... Z -> 26 AA -> 27 AB -> 28 ... Example 1: Input: columnTitle = "A" Output: 1 Example 2: Input: columnTitle = "AB" Output: 28 Example 3: Input: columnTitle = "ZY" Output: 701 Example 4: Input: columnTitle = "FXSHRXW" Output: 2147483647 Constraints: 1 <= columnTitle.length <= 7 columnTitle consists only of uppercase English letters. columnTitle is in the range ["A", "FXSHRXW"].