e-olymp
Problems

Degree of two

Degree of two

n degrees of number 2 are written sequentially in a line, i.e. the numbers from 2 to 2n without spaces. Find the value of n.

Input

n (1n1000) degrees of number 2 are written sequentially in a line.

Output

Print the value of n.

Time limit 1 second
Memory limit 128 MiB
Input example #1
248163264128
Output example #1
7