#include "stdio.h"

int check_5(int x){
	int i = 0;
	while( x%5 == 0){
		i = i + 1;
		x = x/5;
	}
	return i;
}

int main(){

	int x;
	int i,n,nn;
	FILE *fptr;
	fptr = fopen("fact.in", "r");
	fscanf(fptr,"%d",&x);
	i = 0;
	n = 0;
	while(i < x){
		n += 5;
		i = i + check_5(n);
	}
	if(i > x){
		n = -1;
	}
	fclose(fptr);
	fptr = fopen("fact.out", "w");
	fprintf(fptr,"%d\n",n);

	return 0;
}