#include <iostream>
#include <fstream>
using namespace std;
ifstream fin("fact.in");
ofstream fout("fact.out");
int main()
{
    int n,nrz=0,i=0,a[101];
    fin>>n;
    while(nrz<n){
        i++;
        for(int j=1;j<=i;j++){
            a[i]=i;
            if((i*a[j])%10==0||a[j]%10==0){
                nrz++;
                a[i]=-1;
                a[j]=-1;
                j=i;
            }
        }
    }
    fout<<i;
    return 0;
}