#include<stdio.h>
#include<values.h>
int main()
{long long unsigned x=1,pr,n,p,i,j,m,nr;
FILE *f=fopen("fact.in","r");
FILE*g=fopen("fact.out","w");
fscanf(f,"%llu",&p);
if (p==0) fprintf(g,"1");
else {
i=0;
j=MAXLONG;
while (i<=j)
	{ m=(i+j)/2;
	nr=0;  pr=5;
	while(m/pr!=0) {nr+=m/pr; pr*=5;}
	if (nr==p)
	       {while(m%5!=0)
		{m--;
	       if (m%5==0)  {fprintf(g,"%llu",m); break;}}
	       x=0;
	       break;}
	else if (nr<p) i=m+1;
	else j=m-1;}
if (x) fprintf(g,"-1"); }
fclose(f);
fclose(g);
return 0;}