alfabetar.cpp: In function 'int main()': alfabetar.cpp:16: warning: comparison between signed and unsigned integer expressions alfabetar.cpp:9: warning: ignoring return value of 'FILE* freopen(const char*, const char*, FILE*)', declared with attribute warn_unused_result alfabetar.cpp:12: warning: ignoring return value of 'int scanf(const char*, ...)', declared with attribute warn_unused_result alfabetar.cpp:15: warning: ignoring return value of 'char* gets(char*)', declared with attribute warn_unused_result In file included from /usr/include/stdio.h:910, from /usr/include/c++/4.4/cstdio:45, from alfabetar.cpp:3: In function 'char* gets(char*)', inlined from 'int main()' at alfabetar.cpp:15: /usr/include/bits/stdio2.h:230: warning: call to '__gets_warn' declared with attribute warning: please use fgets or getline instead, gets can't specify buffer size /tmp/ccsZcOwf.o: In function `main': alfabetar.cpp:(.text+0x1b0): warning: the `gets' function is dangerous and should not be used.