import java.util.Stack;

public class Main {
    public static void main(String[] args) {
        String str = "a<s>b/sc</s>";
        System.out.println(isValid(str));
    }

    public static boolean isValid(String str) {
        Stack<Character> stack = new Stack<>();
        for (int i = 0; i < str.length(); i++) {
            char c = str.charAt(i);
            if (c == '<') {
                if (!stack.isEmpty() && stack.peek() == '/') {
                    stack.pop();
                } else {
                    stack.push('<');
                }
            } else if (c == '>') {
                if (stack.isEmpty()) {
                    return false;
                } else if (stack.pop() == '<') {
                    continue;
                } else {
                    return false;
                }
            } else if (c != '/') {
                stack.push(c);
            }
        }
        return stack.isEmpty();
    }
}