#include <boost/multiprecision/cpp_int.hpp>
#include <iostream>

using boost::multiprecision::cpp_int;

int main() {
  cpp_int n;
  std::cin >> n;

  cpp_int ng = n, ok = 0;
  while (ng - ok > 1) {
    cpp_int mid = (ng + ok) / 2;
    if (mid * mid <= n) {
      ok = mid;
    } else {
      ng = mid;
    }
  }
  size_t ans = ok.str().size();

  std::cout << ans << std::endl;
}