//#include<algorithm>
//using namespace std;
#include<stdio.h>
int p;
void solve(){
    int i,k,x;
	scanf("%d",&p);
	if(p==0)
		printf("1");
	else
		for(i=5; ; i+=5){
			k=0;
			for(x=i; x&&k<p; k+=x/=5);
			if(k==p){
				printf("%d",i);
				break;}}}
int main(){
    freopen("fact.in","r",stdin);
    freopen("fact.out","w",stdout);
    solve();
    return 0;}