def isBalanced(s):
    # Write your code here
    bras = []
    braOpen = set(['(', '[', '{'])
    braClose = {
        ')': '(',
        '}': '{',
        ']': '['
    }
    
    for bra in s:
        if bra in braOpen:
            bras.append(bra)
        elif bra in braClose:
            if not bras or bras[-1] != braClose[bra]:
                return "NO"
            else:
                bras.pop(-1)
    
    return "NO" if bras else "YES"