/in/foo.cc: In function 'int main()':
/in/foo.cc:16:12: warning: comparison between signed and unsigned integer expressions [-Wsign-compare]
  for (i=0;i<strlen(s);i++)
           ~^~~~~~~~~~
/in/foo.cc:19:13: warning: comparison between signed and unsigned integer expressions [-Wsign-compare]
   for (j=i;j<i+strlen(c1);j++)
            ~^~~~~~~~~~~~~
/in/foo.cc:23:14: warning: comparison between signed and unsigned integer expressions [-Wsign-compare]
    for (k=i;k<i+strlen(c1);k++)
             ~^~~~~~~~~~~~~
/in/foo.cc:15:10: warning: unused variable 'n' [-Wunused-variable]
  int i,j,n=0,k=0;
          ^