#include <bits/stdc++.h>
using namespace std;
#include <boost/multiprecision/cpp_int.hpp>
typedef boost::multiprecision::cpp_int mp;

int main(){
    int x;
    double ans=0;
    cin>>x;
    auto start=std::chrono::system_clock::now();
    auto end=std::chrono::system_clock::now();
    int msec=std::chrono::duration_cast<std::chrono::milliseconds>(end-start).count();
    while(msec<1900){
        ans+=std::riemann_zeta(x)-1;
        ++x;
        end=std::chrono::system_clock::now();
        msec=std::chrono::duration_cast<std::chrono::milliseconds>(end-start).count();
    }
    ans*=1000000;
    cout<<floor(ans)<<endl;
}