#include <stdio.h>

int p;

int nr(int k){
int temp=0,i=5;



while(i<=k){temp+=k/i;i*=5;}

return temp;

}


int bs(int lo,int hi){
int mid;

while(lo<hi){
mid=lo+(hi-lo)/2;
if(nr(mid)>=p){hi=mid;}else{lo=mid+1;}

}

if(nr(lo)==p){return lo;}else{return -1;}

}

int main(){
	freopen("fact.in","r",stdin);
	freopen("fact.out","w",stdout);
	scanf("%d",&p);
	int i=1;
	if(p==0){printf("1");}else{
	

	printf("%d",bs(0,5*p));
	}

	return 0;}