#include <stdio.h>
#define INFILE "fact.in"
#define OUTFILE "fact.out"

int P;

int fact(int N)
{
	int p = 5;
	int count = 0;
	while (p<=N) {
		count += N/p;
		p = p*5;
	}
	return count;
}

int cauta(int target, int low, int high)
{
	int mid, count;
	while (low < high) {
		mid = (low + high)/2;
		count = fact(mid);
		if (target == count)
			return mid;		
		if (target < count) 
			high = mid-1;
		else
			low = mid+1;
	}
	return -1;
}
	

int main()
{
	freopen(INFILE, "r", stdin);
	freopen(OUTFILE, "w", stdout);
	scanf("%d", &P);
	if (P == 0) {
		printf("1");
		return 0;
	}
	int low = 0;
	int high = 400020000; 
	int result = cauta(P, low, high);
	if (result == -1) {
		printf("-1");
		return 0;
	}
	result = result/5*5;
	printf("%d\n", result);
	return 0;
}