  This paper describes a linear-time algorithm that finds the longest stretch
in a sequence of real numbers (``scores'') in which the sum exceeds an input
parameter. The algorithm also solves the problem of finding the longest
interval in which the average of the scores is above a fixed threshold. The
problem originates from molecular sequence analysis: for instance, the
algorithm can be employed to identify long GC-rich regions in DNA sequences.
The algorithm can also be used to trim low-quality ends of shotgun sequences in
a preprocessing step of whole-genome assembly.
