Combine the given two facts to write a concluding fact. Note that there should be some parts of the first and second facts that are not mentioned in this conclusion fact. Your combined fact should be the result of a chain between the two facts. Chains form when two facts connect together to produce a concluding fact. An example of a chain is: "pesticides cause pollution" (fact1) + "pollution can harm animals" (fact2) → "pesticides can harm animals" (conclusion fact). Parts of the concluding fact overlap with the first and the second fact. To construct such a  concluding fact, a useful way is to borrow the subject from one fact and the ending conclusions from another fact.

Input: Consider Input: Fact 1: Pneumonia may be caused by an infection or injury of the lungs. 
Fact 2: Infections of the lungs can be caused by bacteria, viruses or fungi.

Output: Pneumonia may be caused by viruses or injury.


Input: Consider Input: Fact 1: a compass is used to navigate oceans. 
Fact 2: Ocean waves travel on the surface of the water.

Output: A compass is used to travel on the surface of the water.


Input: Consider Input: Fact 1: condensation causes clouds to form. 
Fact 2: Fog is a cloud that forms on the ground.


Output: condensation causes fog.