#include<iostream>
#include<stdio.h>
FILE *f,*g;
int main ()
{
f=fopen("fact.in","r");
g=fopen("fact.out","w");
int p,n=0,nr=0,n1;
fscanf(f,"%d",&p);
if(!p) fprintf(g,"1");
else {
while(nr<p)
{
n++;n1=n;
while(!(n1%5))
{nr++;
 n1/=5;}
}
if(nr==p) fprintf(g,"%d",n); 
else fprintf(g,"-1");
}
fclose(f); fclose(g);
return 0;
}