JEE Main 2022 · 28 Jun · Shift 1, Mathematics question 27

Let $A=\{1,a_1,a_2,\dots,a_{18},77\}$ be a set of integers with $1<a_1<a_2<\dots<a_{18}<77$. Let the set $A+A=\{x+y:x,y\in A\}$ contain exactly 39 elements. Then, the value of $a_1+a_2+\dots+a_{18}$ is equal to ______.