foo.cc: In function 'size_t LCS(size_t, size_t)':
foo.cc:21:23: warning: comparison between signed and unsigned integer expressions [-Wsign-compare]
     for (int i = 1; i <= len1; i++)
                     ~~^~~~~~~
foo.cc:22:27: warning: comparison between signed and unsigned integer expressions [-Wsign-compare]
         for (int j = 1; j <= len2; j++)
                         ~~^~~~~~~

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