Problem:
Score : 300 points

Problem Statement

You are given an integer N.

For two positive integers A and B, we will define F(A,B) as the larger of the following: the number of digits in the decimal notation of A, and the number of digits in the decimal notation of B.

For example, F(3,11) = 2 since 3 has one digit and 11 has two digits.

Find the minimum value of F(A,B) as (A,B) ranges over all pairs of positive integers such that N = A \times B.

Constraints

1 \leq N \leq 10^{10}

N is an integer.

Input

The input is given from Standard Input in the following format:

N

Output

Print the minimum value of F(A,B) as (A,B) ranges over all pairs of positive integers such that N = A \times B.

Sample Input 1

10000

Sample Output 1

3

F(A,B) has a minimum value of 3 at (A,B)=(100,100).

Sample Input 2

1000003

Sample Output 2

7

There are two pairs (A,B) that satisfy the condition: (1,1000003) and (1000003,1). For these pairs, F(1,1000003)=F(1000003,1)=7.

Sample Input 3

9876543210

Sample Output 3

6

Solution in Rust (1.15.1) (judge verdict: Accepted)

#![allow(unused, non_snake_case, dead_code, non_upper_case_globals)]
use std::cmp::*;
use std::collections::*;
use std::mem::*;
//nの約数列挙
pub fn divisor(n: usize) -> Vec<usize> {
    let mut res = Vec::new();
    for i in (1..).take_while(|x| x * x <= n) {
        if n % i == 0 {
            res.push(i);
            if i != n / i {
                res.push(n / i);
            }
        }
    }
    res
}
fn main() {
    let (r, w, e) = (std::io::stdin(), std::io::stdout(), std::io::stderr());
    let mut io = IO::new(r.lock(), w.lock(), e.lock());
    assert_eq!(!0usize, std::usize::MAX); //🙊
    assert!(0 == 0); //😇

    let n = io.read::<usize>();
    let dvs = divisor(n);
    let mut ans = INF;
    for &dv in &dvs {
        let dv2 = n / dv;
        ans = min(ans, f(dv as i64, dv2 as i64));
    }
    io.writeln(ans);

    // a>b のとき、f(a,b) >= となる
}
fn f(a: i64, b: i64) -> i64 {
    let mut ret = 0;
    let mut a = a;
    let mut b = b;
    while a > 0 || b > 0 {
        ret += 1;
        a /= 10;
        b /= 10;
    }
    return ret;
}

static MX: usize = 1010101;
static MOD: i64 = 1000000007;
static INF: i64 = std::i64::MAX >> 1;
// IO
use std::io::*;
struct IO<R: Read, W: Write, E: Write> {
    Read: R,
    Write: BufWriter<W>,
    Error: BufWriter<E>,
}
impl<R: Read, W: Write, E: Write> IO<R, W, E> {
    fn new(r: R, w: W, e: E) -> IO<R, W, E> {
        IO {
            Read: r,
            Write: BufWriter::new(w),
            Error: BufWriter::new(e),
        }
    }
    fn read<T>(&mut self) -> T
    where
        T: std::str::FromStr,
    {
        let next: String = self
            .Read
            .by_ref()
            .bytes()
            .map(|c| c.unwrap() as char)
            .skip_while(|c| c.is_whitespace())
            .take_while(|c| !c.is_whitespace())
            .collect();
        next.parse().ok().unwrap()
    }
    fn chars(&mut self) -> Vec<char> {
        self.read::<String>().chars().collect()
    }
    fn chari(&mut self) -> Vec<i64> {
        self.chars()
            .iter()
            .map(|&c| (c as u8 - b'0') as i64)
            .collect::<Vec<i64>>()
    }
    fn readn<T: std::str::FromStr>(&mut self, n: usize) -> Vec<T> {
        (0..n).map(|_| self.read::<T>()).collect::<Vec<_>>()
    }
    fn readmat<T: std::str::FromStr>(&mut self, n: usize, m: usize) -> Vec<Vec<T>> {
        (0..n).map(|_| self.readn(m)).collect()
    }
    fn write<S: ToString>(&mut self, val: S) {
        self.Write.write(val.to_string().as_bytes());
    }
    fn writeln<S: ToString>(&mut self, val: S) {
        self.Write.write(val.to_string().as_bytes());
        self.Write.write(b"\n");
    }
    fn debug<S: std::fmt::Debug>(&mut self, val: S) {
        writeln!(self.Error, "(debug) {:?}", &val);
    }
    fn debug2<S: std::fmt::Debug, T: std::fmt::Debug>(&mut self, val1: S, val2: T) {
        writeln!(self.Error, "(debug2) {:?} -> {:?}", val1, val2);
    }
    fn debug3<S: std::fmt::Debug, T: std::fmt::Debug, U: std::fmt::Debug>(
        &mut self,
        val1: S,
        val2: T,
        val3: U,
    ) {
        writeln!(
            self.Error,
            "(debug3) {:?} -> {:?} -> {:?}",
            val1, val2, val3
        );
    }
}