Integer Disguised as String

Problem Description

Write a function that accepts a string and returns true if it contains only numbers, i.e., the digits 0 through 9.

Input

• A single string.

Output

• A boolean value: true if the string contains only digits 0 through 9, false otherwise.

Constraints

• The input string may be of any length, including zero.
• The function should not consider leading zeros or large numbers as invalid as long as they contain only digits.

Example

Input:
"01010101"

Output:
true

Explanation:
The string "01010101" contains only digits.

Input:
"123456789"

Output:
true

Explanation:
The string "123456789" contains only digits.

Input:
"9223372036854775808"

Output:
true

Explanation:
The string "9223372036854775808" contains only digits.

Input:
"1.01"

Output:
false

Explanation:
The string "1.01" contains a decimal point, which is not a digit.