#include<bits/stdc++.h>
using lint=long long;
int main(){
    std::cin.tie(nullptr);std::ios_base::sync_with_stdio(false);
    std::cout.setf(std::ios_base::fixed);std::cout.precision(15);
    std::string s="1234567891011121314151617181920212223242526272829303132333435363738394041424344454647484950515253545556575859606162636465666768697071727374757677787980818283848586878889909192939495969798991";
    lint n=s.length();
    std::vector<lint>a;
    for(char c:std::string(s.rbegin(),s.rend())){
        a.push_back(c-'0');
    }
    lint d;std::cin>>d;
    lint carry=0;
    for(lint i=0;i<n;i++){
        a.at(i)=a.at(i)*d+carry;
        carry=a.at(i)/10;
        a.at(i)%=10;
    }
    for(;carry;carry/=10){
        a.push_back(carry%10);
    }
    std::reverse(a.begin(),a.end());
    s.clear();
    std::transform(a.begin(),a.end(),std::back_inserter(s),[](lint x){return '0'+x;});
    s.insert(s.end()-n,'.');
    if((lint)s.length()==n+1)s.insert(s.begin(),'0');
    std::cout<<s<<'\n';
}