/in/foo.cc: In function 'int main()':
/in/foo.cc:9:23: warning: comparison between signed and unsigned integer expressions [-Wsign-compare]
     for (int i = 0; i < in1.size(); ++i) {
                     ~~^~~~~~~~~~~~
/in/foo.cc:14:23: warning: comparison between signed and unsigned integer expressions [-Wsign-compare]
     for (int i = 0; i < str.size(); ++i) cout << m1[str[i]];
                     ~~^~~~~~~~~~~~