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

#define in "fact.in"
#define out "fact.out"

int main()
{
	FILE * fi = fopen(in, "r");
	FILE * fo = fopen(out, "w");

	unsigned long p, N;
	fscanf(fi, "%lu", &p);

	N = 0;

	unsigned long i, j;

	for(i=1;N<p;i++){
		j = i;
		while(j%5){
			N++;
			j /= 5;
		}
	}

	if(N!=p)i = -1;
	fprintf(fo, "%lu", i);

	fclose(fi);
	fclose(fo);
	return 0;
}