#include<stdio.h>

int zerouri(int x)
{
	int z=0;
	while(x)
	{
		z+=x/5;
		x/=5;
	}
	return z;
}

int main()
{
	FILE* f1,*f2;
	f1=fopen("prim.in","r");
	f2=fopen("prim.out","w");
	int p;
	fscanf(f1,"%d",&p);

	int st=1,dr=1000000010;
	while(st<=dr)
	{
		int m=(st+dr)/2;
		if(zerouri(m)<p)
			st=m+1;
		else dr=m-1;
	}
	if(zerouri(st)==p)
		fprintf(f2,"%d\n",st);
	else fprintf(f2,"-1\n");

	return 0;
}