#include <stdio.h>

long long get5(long long nr){
	long long ans=0;
	for(long long k=5;k<=nr;k*=5){
		ans+=nr/k;
	}
	return ans;
}

int main(){
	freopen("fact.in","r",stdin);
	freopen("fact.out","w",stdout);
	int p;
	scanf("%d",&p);
	if(p==0){printf("1");return 0;}
	
	long long st=1,dr=20000000000;
	while(st<dr){
		long long m = (st+dr)/2;
		
		long long g5=get5(m);
		//if(g5==p){printf("%d",m);return 0;}
		if(p<=g5){
			dr=m;
		} 
		else{
			st=m+1;
		}
	}
	if(get5(st)!=p)
		printf("-1");
		else
		printf("%d",st);
	return 0;
}