#include<bits/stdc++.h>

using namespace std;
using ll = long long;
using pint = pair<int,int>;

#include <boost/multiprecision/cpp_int.hpp>
#include <boost/multiprecision/cpp_dec_float.hpp>
namespace mp = boost::multiprecision;
using Int = mp::cpp_int;                        // 任意長整数

Int sqint(Int num){

	Int l = 0;
	Int r = num;

	while(r - l > 1){
		Int mid = (r + l) / 2;
		(mid * mid <= num ? l : r) = mid;
	}
	return l;
}


int main()
{
	Int N; cin >> N;
	auto sq = sqint(N);
	auto str = sq.str();
	cout << str.size() << endl;
}