Compilare: user.cpp: In function ‘int main()’: user.cpp:12:31: warning: ignoring return value of ‘FILE* freopen(const char*, const char*, FILE*)’, declared with attribute warn_unused_result [-Wunused-result] freopen("barbar.in","r",stdin); ^ user.cpp:13:33: warning: ignoring return value of ‘FILE* freopen(const char*, const char*, FILE*)’, declared with attribute warn_unused_result [-Wunused-result] freopen("barbar.out","w",stdout); ^ user.cpp:14:21: warning: ignoring return value of ‘int scanf(const char*, ...)’, declared with attribute warn_unused_result [-Wunused-result] scanf("%d %d",&n,&m); gets(s[0]); ^ user.cpp:14:33: warning: ignoring return value of ‘char* gets(char*)’, declared with attribute warn_unused_result [-Wunused-result] scanf("%d %d",&n,&m); gets(s[0]); ^ user.cpp:17:17: warning: ignoring return value of ‘char* gets(char*)’, declared with attribute warn_unused_result [-Wunused-result] gets(s[i]+1); ^ In file included from /usr/include/stdio.h:934:0, from user.cpp:1: In function ‘char* gets(char*)’, inlined from ‘int main()’ at user.cpp:17:17: /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/ccLRE86I.o: In function `main': user.cpp:(.text.startup+0xc8): warning: the `gets' function is dangerous and should not be used. user.cpp:(.text.startup+0x72): warning: the `gets' function is dangerous and should not be used.