#include<stdio.h>

int main()
{
 FILE *f,*g;
 long int p;
	f=fopen("fact.in","r");
	g=fopen("fact.out","w");
	fscanf(f,"%ld",&p);
	if(p==0) {fprintf(g,"%d",1);return;}
	long int ps=p*5,d=0;
	if(ps%25==0)
		while(ps!=25)
			 {ps=ps-25; d++;}
	long int n=p*5-5*d;
	fprintf(g,"%ld",n);
	fclose(f);
	fclose(g);
	return 0;

}