#include <stdio.h>

int main() {
	freopen("flip.in", "rt", stdin);
	freopen("flip.out", "wt", stdout);
	long p, n = 0, actual = 0;
	short factors[11] = {0}, top = 0;
	
	scanf("%d", &p);
	while (actual < p) {
		n += 5;
		factors[top]++;
		if(factors[top] == 0)
			top++;
		if(factors[top] == 1 && top != 0)
			top--;
		actual += top + 1;
	}
	
	printf("%d", actual == p ? n : -1);
	return 0;
}