#include <bits/stdc++.h>
using namespace std;
ifstream fin("fact.in");
ofstream fout("fact.out");

int main(){
long long nr=1,prod,p;
int numaratoare=0;
cin>>p;
while(p>numaratoare){
for(int i=1;i<=nr;i++)
   prod=prod*i;

   numaratoare=0;
   while(prod%10==0)
   {

       if(prod%10==0)
       {
        numaratoare++;
        prod=prod/10;
       }

   }
   if (numaratoare==p)
cout<<nr;

else {nr++;
prod=1;
}
}
}