#include<fstream.h>
ifstream fin("factorial.in");
ofstream fout("factorial.out");
unsigned p,k,n,search,rev;
int main(){
	fin>>p;
	k=0;
	n=0;
	while(p>n){
		k=k+5;
		rev=k;
		while(k!=0){
			search=k/5;
			if(search*5==k) n++;
			k=k/5;
		}
		k=rev;
	}
	fout<<k;
	fin.close();
	fout.close();
	return 0;
}