foo.cc: In function 'int main()':
foo.cc:25:15: warning: comparison of integer expressions of different signedness: 'int' and 'size_t' {aka 'long unsigned int'} [-Wsign-compare]
   25 |  for(int i=0;i<strlen(a);i++)
      |              ~^~~~~~~~~~
foo.cc:28:19: warning: comparison of integer expressions of different signedness: 'int' and 'size_t' {aka 'long unsigned int'} [-Wsign-compare]
   28 |    for(int j=i+1;j<strlen(a);j++)
      |                  ~^~~~~~~~~~

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