#include <cstdio>

long long nz(long p){
	
}

int main(){
	long n;
	long t,ct;
	long long i,r,l,m;
	
	freopen("factorial.in","rt",stdin);
	freopen("factorial.out","wt",stdout);
	
	scanf("%ld",&n);
	
	l=1;
	r=0xffffff;
	
	while(l<r){
		m=(l+r)/2;
		ct=0;
		for(i=5;i<=m;i+=5){
			t=i;
			while(!(t%5)){
				ct++;
				t/=5;
			}
		}
		if(n==ct){
			for(;m%5;m--);
			if(m==0)
				m++;
			printf("%lld",m);
			return 0;
		}
		else if(n>ct)
			l=m+1;
		else
			r=m;
	}
	
	printf("-1");
	return 0;
	
}