What is the minimum age of voter required according to the 1973 constitution?

ELIGIBILITY TO BE A VOTER\nA person, who is a citizen of Pakistan, is not less than 18 years of age on the first day of January of the year in which the rolls are prepared or revised, is not declared by a competent court to be of unsound mind and is or is deemed to be a resident of an electoral area, can get himself enrolled as a voter in that electoral area.\nOnly citizens registered on the Electoral Rolls are eligible to cast their votes.