#include <stdio.h>
#include <stdlib.h>

int main(){

	FILE *fp, *fr;
	long p, zeros = 0, n, i = 0, result = 0;

	fp = fopen("fact.in","r");
	fr = fopen("fact.out", "w");

	fscanf(fp, "%ld", &p);
	fclose(fp);
	

	while(zeros != p){

		if(zeros > p) {
			result = -1;
			break;
		}

		i++;
		n = i;
		result = n;

		while(n % 5 == 0){		
			n /= 5;
			zeros++;
		}
	}

	fprintf(fr, "%ld", result);
	
	fclose(fr);

	return 0;
}