#include <algorithm>
#include <iomanip>
#include <array>
#include <bitset>
#include <cassert>
#include <cmath>
#include <cstdio>
#include <deque>
#include <functional>
#include <iostream>
#include <iterator>
#include <map>
#include <queue>
#include <set>
#include <string>
#include <sstream>
#include <unordered_map>
#include <unordered_set>
#include <utility>
#include <numeric>
#include <vector>
using namespace std;
#if __has_include(<atcoder/all>)
#include <atcoder/all>
using namespace atcoder;
#endif
#define GET_MACRO(_1, _2, _3, NAME, ...) NAME
#define _rep(i, n) _rep2(i, 0, n)
#define _rep2(i, a, b) for(int i = (int)(a); i < (int)(b); i++)
#define rep(...) GET_MACRO(__VA_ARGS__, _rep2, _rep)(__VA_ARGS__)
#define all(x) (x).begin(), (x).end()
#define rall(x) (x).rbegin(), (x).rend()
using i64 = long long;
template<class T, class U>
bool chmin(T& a, const U& b) { return (b < a) ? (a = b, true) : false; }
template<class T, class U>
bool chmax(T& a, const U& b) { return (b > a) ? (a = b, true) : false; }

template<typename T>istream& operator>>(istream&i,vector<T>&v){rep(j,v.size())i>>v[j];return i;}
template<typename T>string join(vector<T>&v){stringstream s;rep(i,v.size())s<<' '<<v[i];return s.str().substr(1);}
template<typename T>ostream& operator<<(ostream&o,vector<T>&v){if(v.size())o<<join(v);return o;}
template<typename T>string join(vector<vector<T>>&vv){string s="\n";rep(i,vv.size())s+=join(vv[i])+"\n";return s;}
template<typename T>ostream& operator<<(ostream&o,vector<vector<T>>&vv){if(vv.size())o<<join(vv);return o;}
template<class T> using pq = priority_queue<T, vector<T>, greater<T>>;

i64 solve(i64 n)
{
    i64 ans = 0;
    vector<i64> prime(7500, true); // 素数かどうか？
    vector<i64> x(n + 1); // 指数が奇数であるものの積
    rep(i, n + 1) x[i] = i;
    i64 i = 2;
    while(i * i <= n)
    {
        if(prime[i])
        {
            i64 w = i * i;
            i64 j = w; 
            while(j * j <= n) // エラストテネスの篩
            {
                prime[j] = false; // 素数でない
                j += i;
            }

            j = w;
            while(j <= n) // p^2, p^4, p^6, ... 
            {
                i64 k = j; // p^2, p^4, ...
                while(k <= n)
                {
                    x[k] /= w;
                    k += j; // p^2 -> 2 * p^2, p^4 -> 2 * p^4, ...
                }
                j *= w;
            }
        }
        i++;
    }
    for (i = 1; i < n + 1; i++)
    {
        ans += sqrt(n / x[i]);
    }
    return ans;
}


int main()
{
    i64 n;
    cin >> n;
    cout << solve(n) << endl;
    return 0;
}