#include <stdio.h>
#include <math.h>

long long int P,p,nr,ind;

int main(){
	
	freopen("fact.in","r",stdin);  
	freopen("fact.out","w",stdout);

    scanf("%llu\n", &P);
    	
    if (P%5 != 0)
    {
    	while (p < P)
    	{
        	nr += 5;
        	ind = nr;
       	 	while (ind % 5 == 0)
        	{
            	ind = ind / 5;
            	p++;
        	}
    	}
    	if (P==0) nr=1;
    	
    	    	
    	
    }
    
    else nr = -1;
    

    printf("%lli\n", nr);

}