Compilare: user.cpp: In function ‘int main(int, const char**)’: user.cpp:11:35: warning: ignoring return value of ‘FILE* freopen(const char*, const char*, FILE*)’, declared with attribute warn_unused_result [-Wunused-result] freopen ("drum6.in","r",stdin); ^ user.cpp:12:37: warning: ignoring return value of ‘FILE* freopen(const char*, const char*, FILE*)’, declared with attribute warn_unused_result [-Wunused-result] freopen ("drum6.out","w",stdout); ^ user.cpp:14:26: warning: ignoring return value of ‘int scanf(const char*, ...)’, declared with attribute warn_unused_result [-Wunused-result] scanf("%d%d\n",&N,&M); -- N , -- M; ^ user.cpp:16:20: warning: ignoring return value of ‘char* gets(char*)’, declared with attribute warn_unused_result [-Wunused-result] gets (V[i]); ^ In file included from /usr/include/stdio.h:934:0, from user.cpp:3: In function ‘char* gets(char*)’, inlined from ‘int main(int, const char**)’ at user.cpp:16:20: /usr/include/i386-linux-gnu/bits/stdio2.h:230:28: warning: call to ‘__gets_warn’ declared with attribute warning: please use fgets or getline instead, gets can't specify buffer size [enabled by default] return __gets_warn (__str); ^ /tmp/ccTF5HN1.o: In function `main': user.cpp:(.text.startup+0x8d): warning: the `gets' function is dangerous and should not be used.