compare totals and provide a result

I have a simple query, which needs resolution.

I want to compare totals in row 2, columns A, B and C and the result is to be the lowest amount, but can't be zero.
Column A will always have a number value, columns B and C may be of lesser value or even zero - however only one of B or C will have an amout, they will never both contain an amount at the same time.

So if both B and C are Zero, produce result of A, if B or C have an amount give the lowest amount.

A - B - C - D
45 - 10 - 0 result 10
80 - 0 - 20 result 20
45 - 0 - 0 result 45

Any ideas?

Not sure if this will work, works on your test data you might want to test other values

=MIN(IF(A1:C1>0,A1:C1))

Note: array formula, use Ctrl-Shift-Enter