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

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

do{
n++;
n5=n;
if (n%5==0)
{while(n5 % 5==0)
 {
 p5++;
 n5=n5/5;
 }
} else;
 }
while (p5<p);


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

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