A lucky year is one in which at least one date, when written in the form month/day/year, has the following property: The product of the month times the day equals the last two digits of the year. For example, $1956$ is a lucky year because it has the date $7/8/56$ and $7\times 8 = 56$. Find the year from the following list that is NOT a lucky year: 1990, 1991, 1992, 1993, 1994.

Let's think step by step and output the final answer within \boxed{}.
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