@S3.to_S1.{1} nat (@S4.to_S3.{1} nat s) =?= f.{1} nat (@S4.to_S2.{1} nat s)
@S3.to_S1.{1} nat (@S4.to_S3.{1} nat s) =?= f.{1} nat (@S4.to_S2.{1} nat s)
success
@S3.to_S1.{1} nat (@S4.to_S3.{1} nat s) =?= @S2.to_S1.{1} nat (@S4.to_S2.{1} nat s)
@S3.to_S1.{1} nat (@S4.to_S3.{1} nat s) =?= @S2.to_S1.{1} nat (@S4.to_S2.{1} nat s)
success