Task: Question Answering
Input (English): Question: The reordering of Cope is a reordering: 
 Options:  <1> From an allyl vinyl ether. <2> [1,3] -sigmatropic. <3> [1,2] -sigmatropic. <4> [3,3] -sigmatropic. <5> It is a cycloaddition [4 + 2].
Output (English): 4