Decode Encoded Message

You are given an encoded message consisting of alternating letters and digits. Each letter is immediately followed by a single digit, representing how many times that letter should appear in the decoded message.

The encoded string must follow the pattern:

[ S = L_1D_1L_2D_2\ldots L_kD_k ]

where each \(L_i\) is an alphabet character (a-z or A-Z) and each \(D_i\) is a single digit (0-9). The string is considered invalid if:

• The string is empty.
• The string length is odd.
• A letter is not immediately followed by a digit.

If the input is invalid, output Invalid Input. Otherwise, expand each letter by the number of times indicated by the following digit.

Examples:

• Input: a3b4c2 → Output: aaabbbbcc
• Input: x1y1 → Output: xy
• Input: a2b → Output: Invalid Input

inputFormat

The input is read from stdin and consists of a single line string representing the encoded message.

outputFormat

The output should be written to stdout as a single line. It is either the decoded message or the string Invalid Input if the input format is incorrect.

## sample

a3b4c2

aaabbbbcc