#include <stdio.h>

int main()
{
	FILE* f=fopen("fact.in","r");
	FILE* g=fopen("fact.out","w");
	int n,i,ver;
	
	fscanf(f,"%d", &n);
	fclose(f);
	if (n!=0)
		for (i=5;n;i+=5){
			ver=5;
			do {
				n--;
				ver*=5;
			}while ((i%ver==0) && (n));
		}
	else 
		i=6;
	fprintf(g,"%d", i-=5);
	fclose(g);
	return 0;
}