def onize_formula(formula=""):
    """
    Chemical formulas don't show ones like H2O1, it ignores numbers when it's equal to one.
    For consistency, we're adding those ones here.
    input: str
    output: str
    This function is idempotent
    """
    formula_with_ones = []
    for element in formula:
        if element.isdigit():
            formula_with_ones.append(element)
        elif element.islower():  # means that it's part of the previous element name
            formula_with_ones.append(element)
        else:
            if formula_with_ones and not formula_with_ones[-1].isdigit() and formula_with_ones[-1] not in ['(', '[']:
                formula_with_ones.append('1')
            formula_with_ones.append(element)

    if not formula_with_ones[-1].isdigit():
        formula_with_ones.append('1')
    return ''.join(formula_with_ones)