#include<fstream>
using namespace std;
ifstream f("factorial.in");
ofstream g("factorial.out");

int main()
{ long long p;
    f>>p;
    long long numar,i;
    numar=1;  i=1;
    long long fact;
    long long k=0;
    long long zero=1;

 f>>p;
 while(k!=p){zero=zero*10;
			 k++;
			}
 while(numar%zero!=0){numar=numar*i;
					 i++;
					 if(numar%zero==0)fact=i;
					 }
 fact--;
 g<<fact;

 return 0;
}