/in/foo.cc: In function 'int main()':
/in/foo.cc:11:23: warning: comparison between signed and unsigned integer expressions [-Wsign-compare]
     for (int i = 0; i < row; i++)
                     ~~^~~~~
/in/foo.cc:14:27: warning: comparison between signed and unsigned integer expressions [-Wsign-compare]
         for (int j = 0; j < column; j++)
                         ~~^~~~~~~~
/in/foo.cc:24:23: warning: comparison between signed and unsigned integer expressions [-Wsign-compare]
     for (int k = 0; k < row; k++)
                     ~~^~~~~
/in/foo.cc:26:27: warning: comparison between signed and unsigned integer expressions [-Wsign-compare]
         for (int i = 0; i < column; i++)
                         ~~^~~~~~~~
/in/foo.cc:30:31: warning: comparison between signed and unsigned integer expressions [-Wsign-compare]
         for (int len = 1; len <= column; len++)
                           ~~~~^~~~~~~~~
/in/foo.cc:32:31: warning: comparison between signed and unsigned integer expressions [-Wsign-compare]
             for (int i = 0; i < column - len; i++)
                             ~~^~~~~~~~~~~~~~