#include<cstdio>
using namespace std;
long long int put5[15];
long long int p,nr,i,j,ad=1,af,sc,aux;
int main(){
	freopen("factorial.in","r",stdin);
	freopen("factorial.out","w",stdout);
	scanf("%d",&p);
	aux=p;
	nr=0;
	for(i=2,put5[1]=5;i<=13;++i){
		put5[i]=put5[i-1]*5;
		for(j=1;j<i;++j,++nr){
			if(p==put5[i-1]+nr){
				ad=0;
				break;
			}
		}
		if(put5[i]<aux*5){
			aux-=(i-1);
		}
	}
	if(ad==0){
		printf("-1");
	}
	else{
		p=aux;
		af=p*5;
		printf("%d",af);
	}
	return 0;
	}