#include<stdio.h>
int main()
{
unsigned int  n2,n5,p,n=0,p2=0, p5=0;

FILE *f;
f=fopen("fact.in","r");
fscanf(f,"%d\n",&p);
fclose(f);

do{
n++;
n2=n;
while(!(n2%2)){
p2++;
n2=n2/2;}
n5=n;
while(!(n5%5)){
n5=n5/5;}
}while (p5<p);


f=fopen("fact.out","w");

n = ((!p)?1:n);
if ((p2==p) && (p2==p5))
fprintf(f, "%d", n);
else
fprintf(f,"-1");
fclose(f);
return 0;
}