Given a string, determine whether or not the string contains only digits.

Input Specification

There will be a single line of input, containing a single string with no spaces.

Output Specification

Output yes if the string contains only digits, or no if it does not.

Sample Input 1

9234120

Sample Output 1

yes

Sample Input 2

P1ease_h3lp_I_am_J0nath@n_aNd_I_am_v3rY_l0nely_:(

Sample Output 2

no