/in/ex3.cpp: In function 'void encrypt(int, const char*)':
/in/ex3.cpp:53:18: error: comparison between signed and unsigned integer expressions [-Werror=sign-compare]
     for(i = 0; i < sentence.length(); i++)
                ~~^~~~~~~~~~~~~~~~~~~
cc1plus: all warnings being treated as errors
/in/compile/Makefile:20: recipe for target 'ex3.o' failed
make: *** [ex3.o] Error 1