/in/foo.cc: In function 'int main()':
/in/foo.cc:7:14: warning: comparison between signed and unsigned integer expressions [-Wsign-compare]
 for(int i=0;i<strlen(key);i++)
             ~^~~~~~~~~~~~
/in/foo.cc:10:14: warning: comparison between signed and unsigned integer expressions [-Wsign-compare]
 for(int i=0;i<strlen(A);i++)
             ~^~~~~~~~~~
/in/foo.cc:15:14: warning: comparison between signed and unsigned integer expressions [-Wsign-compare]
 for(int i=0;i<strlen(A);i++){
             ~^~~~~~~~~~
/in/foo.cc:22:14: warning: comparison between signed and unsigned integer expressions [-Wsign-compare]
 for(int i=0;i<strlen(A);i++)
             ~^~~~~~~~~~