agendatelefonica.cpp: In function `void add(int, int)': agendatelefonica.cpp:29: warning: comparison between signed and unsigned integer expressions agendatelefonica.cpp: In function `void prefix(int, int)': agendatelefonica.cpp:45: warning: comparison between signed and unsigned integer expressions /tmp/ccHMcqpz.o(.text+0x289): In function `main': : the `gets' function is dangerous and should not be used.