/in/foo.cc: In function 'void DP()':
/in/foo.cc:30:25: warning: comparison between signed and unsigned integer expressions [-Wsign-compare]
   for (int j = i - 1; j < s[i].length(); j++)
                       ~~^~~~~~~~~~~~~~~
/in/foo.cc:38:21: warning: comparison between signed and unsigned integer expressions [-Wsign-compare]
   for (int j = i; j <= s[i].length(); j = j + 2)
                   ~~^~~~~~~~~~~~~~~~
/in/foo.cc:46:25: warning: comparison between signed and unsigned integer expressions [-Wsign-compare]
   for (int j = i + 1; j <= s[i].length(); j = j + 2)
                       ~~^~~~~~~~~~~~~~~~
/in/foo.cc:28:6: warning: unused variable 'k' [-Wunused-variable]
  int k;
      ^
/in/foo.cc: In function 'int main()':
/in/foo.cc:61:7: warning: unused variable 'ch' [-Wunused-variable]
  char ch[2 * MaxN + 1];
       ^~