#include <cstdio>
using namespace std;

FILE *f=fopen ("fact.in","r");
FILE *g=fopen ("fact.out","w");

int main(){
	int n,p;
	
	fscanf (f,"%d",&n);
	if (5*n>48828125){
		fprintf (g,"%d",5*n-105);
		return 0;
	}
	if (5*n>9765625){
		fprintf (g,"%d",5*n-75);
		return 0;
	}
	if (5*n>1953125){
		fprintf (g,"%d",5*n-50);
		return 0;
	}
	if (5*n>390625){
		fprintf (g,"%d",5*n-30);
		return 0;
	}
	if (5*n>625){
		fprintf (g,"%d",5*n-15);
		return 0;
	}
	if (5*n>25){
		fprintf (g,"%d",5*n-5);
		return 0;
	}
	if (5*n>0){
		fprintf (g,"%d",5*n);
	}
	else{
		fprintf (g,"%d",1);
	}
	
	
	
	
	return 0;
}