solve =. monad define
	ns =. p:i._1 p: y
	for_length. |.I.y>+/\ns do.
		sums =. length+/\ns
		vals =. sums#~(y>sums)*.isPrime sums
		if. 0<#vals do.
			return. >./vals
		end.
	end.
)
problem50 =: solve 1e6