/in/foo.cc: In function 'int main()':
/in/foo.cc:18:20: warning: comparison between signed and unsigned integer expressions [-Wsign-compare]
  for (int i = 0; i < data.size(); i++)
                    ^
/in/foo.cc:20:21: warning: comparison between signed and unsigned integer expressions [-Wsign-compare]
   for (int j = 1; j <= data[i]; j++)
                     ^
/in/foo.cc:22:22: warning: comparison between signed and unsigned integer expressions [-Wsign-compare]
    for (int m = 1; m <= data[i] - j; m++)
                      ^