#include <bits/stdc++.h>
using namespace std;

int main() {
    ios_base::sync_with_stdio(false);
    cin.tie(nullptr);

    long long N; cin >> N;
    vector<int> P = {2,3,5,7,11,13,17,19,23,29,31,37,41,43,47,53};
    __int128_t now = 1;
    for(int i=0; ; i++){
        now *= P.at(i);
        if(now > N){cout << i << endl; return 0;}
    }
}