#include<iostream>
#include<fstream>
using namespace std;
ifstream f("fact.in");
ofstream g("fact.out");
unsigned int OK,i,j,l=0,p,d;
long long t;
int main(){
    f>>p;
   i=1;
   OK=1;
   while(OK!=0){
        t=1;
        l=0;
        for(j=1;j<=i;j++)
            if(j%5==0)
                l++;
            if(l==p){
                    d=i;
            OK=0;}
            i++;}
            g<<d;
            return 0;}