#include <cstdio>

int main()
{
	int n;
	FILE *f1, *f2;
	f1 = fopen("secv.in", "r");
	f2 = fopen("secv.out", "w");
	fscanf(f1, "%d", &n);
	if (n == 0) fprintf(f2, "-1\n");
	fclose(f1);
	fclose(f2);
	return 0;
}