foo.cc: In function 'int main()':
foo.cc:16:15: warning: comparison between signed and unsigned integer expressions [-Wsign-compare]
  for(int i=0;i<strlen(a);i++)
              ~^~~~~~~~~~
foo.cc:18:15: warning: comparison between signed and unsigned integer expressions [-Wsign-compare]
  for(int i=0;i<strlen(b);i++)
              ~^~~~~~~~~~
foo.cc:20:15: warning: comparison between signed and unsigned integer expressions [-Wsign-compare]
  for(int i=0;i<strlen(a);i++)
              ~^~~~~~~~~~
foo.cc:21:15: warning: comparison between signed and unsigned integer expressions [-Wsign-compare]
  for(int j=0;j<strlen(b);j++)
              ~^~~~~~~~~~
foo.cc:31:7: warning: statement has no effect [-Wunused-value]
  for(i;i>=0;i--)
       ^

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