# include <fstream>

using namespace std;

ifstream in("fact.in");
ofstream out("fact.out");

int cinci(int n){
	int r=0;
	while(n%5==0){
		r++;
		n=n/5;
	}
	return r;
}
int main(){
	int n,i,j;
	in>>n;
	i=0;
	j=0;
	while(i<n){
		j=j+5;
		i=i+cinci(j);
	}
	if(n==0){
		out<<"1";
	}else{
		out<<j;
	}
	return 0;
}