foo.cc: In function 'void cf(int)':
foo.cc:20:38: warning: unused variable 'ylen' [-Wunused-variable]
   20 |     int x[500]= {0},y[500]= {0},xlen,ylen,i,j,h;
      |                                      ^~~~
foo.cc:20:47: warning: variable 'h' set but not used [-Wunused-but-set-variable]
   20 |     int x[500]= {0},y[500]= {0},xlen,ylen,i,j,h;
      |                                               ^
foo.cc: In function 'int main()':
foo.cc:61:15: warning: comparison of integer expressions of different signedness: 'int' and 'std::__cxx11::basic_string<char>::size_type' {aka 'long unsigned int'} [-Wsign-compare]
   61 |     for(i=0; i<n.size(); i++) {
      |              ~^~~~~~~~~

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