// yukicoder: No.791 うし数列
// 2019.4.12 bal4u

#include <stdio.h>

int main()
{
	int c, ans;

	if (getchar() != '1') goto ng;
	if (getchar() != '3') goto ng;
	ans = 1;
	while (1) {
		c = getchar();
		if (c < '0') break;
		if (c != '3') goto ng;
		ans++;
	}
	printf("%d\n", ans);
	return 0;
ng: puts("-1");
	return 0;
}