#include<stdio.h>
int main () {
	int p=5,u=5,nr=0,n,x,uc,s;
	FILE *in=fopen("fact.in","r"), *out=fopen("fact.out","w");
	fscanf(in,"%d",&n);
	while(nr<n){
		x=0;
		uc=u;
		while(uc!=1){
			uc/=5;
			x++;
		}
		nr+=((u-p)/5)+x;
		p=u+5;
		u=u*5;
	}
	u/=5;
	s=(nr-n-x+1)*5;
	fprintf(out,"%d",u-s);
	fclose(in);
	fclose(out);
	return 0;
}