Problem:
Score : 100 points

Problem Statement

There are S sheep and W wolves.

If the number of wolves is greater than or equal to that of sheep, the wolves will attack the sheep.

If the wolves will attack the sheep, print unsafe; otherwise, print safe.

Constraints

1 \leq S \leq 100

1 \leq W \leq 100

Input

Input is given from Standard Input in the following format:

S W

Output

If the wolves will attack the sheep, print unsafe; otherwise, print safe.

Sample Input 1

4 5

Sample Output 1

unsafe

There are four sheep and five wolves. The number of wolves is not less than that of sheep, so they will attack them.

Sample Input 2

100 2

Sample Output 2

safe

Many a sheep drive away two wolves.

Sample Input 3

10 10

Sample Output 3

unsafe

Solution in C (GCC 9.2.1) (judge verdict: Wrong Answer)

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

int		g_node_count = 0;

typedef	struct	s_btree
{
	char			*item;
	struct s_btree	*left;
	struct s_btree	*right;
}					t_btree;

t_btree	*btree_create_element(void *str)
{
	t_btree	*ret;

	ret = malloc(sizeof(t_btree));
	ret->item = str;
	ret->left = 0;
	ret->right = 0;
	return (ret);
}

bool	btree_search_item(t_btree *root, void *item)
{
	bool	ret;

	if (!root)
		return (false);
	if ((ret = btree_search_item(root->left, item)))
		return (ret);
	if (!strcmp(root->item, item))
		return (true);
	if ((ret = btree_search_item(root->right, item)))
		return (ret);
	return (false);
}

void	btree_insert_item(t_btree **root, void *item)
{
	if (!*root)
	{
		*root = btree_create_element(item);
		return ;
	}
	if (strcmp((*root)->item, item) < 0)
	{
		if (!(*root)->left)
		{
			(*root)->left = btree_create_element(item);
			return ;
		}
		btree_insert_item(&(*root)->left, item);
	}
	else
	{
		if (!(*root)->right)
		{
			(*root)->right = btree_create_element(item);
			return ;
		}
		btree_insert_item(&(*root)->right, item);
	}
}

void	btree_print_infix(t_btree *root)
{
	if (!root)
		return ;
	btree_print_infix(root->left);
	printf("%s\n", root->item);
	btree_print_infix(root->right);
}

void	btree_count_node(t_btree *root)
{
	if (root->left)
		btree_count_node(root->left);
	g_node_count++;
	if (root->right)
		btree_count_node(root->right);
}

int		main(void)
{
	int		N;
	int		i;
	char	S[200001][11];
	t_btree	*tree;

	scanf("%d", &N);
	for (i = 0; i < N; i++)
		scanf("%s", S[i]);
	tree = 0;
	for (i = 0; i < N;  i++)
	{
		if (!btree_search_item(tree, S[i]))
			btree_insert_item(&tree, S[i]);
	}
	btree_count_node(tree);
	printf("%d\n", g_node_count);
	return (0);
}