#include <stdio.h>

int p,n,numar=0;

int putere(int x)
{int i=0;
while (x%5==0)
	{
	i++;
	x/=5;
	}
return i;
}

int main()
{FILE *pf;
pf=fopen("fact.in","r");
fscanf(pf,"%d",&p);
fclose(pf);
for (n=5;numar<p;n+=5)
	numar+=putere(n);
pf=fopen("fact.out","w");
if (numar==p) fprintf(pf,"%d",n-5);
	else fprintf(pf,"%d",-1);
fclose(pf);
return 0;
}