Let's say the answer is x, then every a_i can be written as x * b_i where b_i ≥ 1

x * b₁ + x * b₂ + ... + x * b_n = m

x(b₁ + b₂ + ... + b_n) = m

therefore m should be divisible by x. So you can try all divisors of m.

Since b_i ≥ 1, then sum of all b_i's should be at least n, i.e.

From all the divisors that satisfy the previous rule, find the maximum one.