Compilare: user.cpp: In function ‘int main()’: user.cpp:18:41: warning: ignoring return value of ‘FILE* freopen(const char*, const char*, FILE*)’, declared with attribute warn_unused_result [-Wunused-result] freopen("interesant.in", "r", stdin); ^ user.cpp:19:43: warning: ignoring return value of ‘FILE* freopen(const char*, const char*, FILE*)’, declared with attribute warn_unused_result [-Wunused-result] freopen("interesant.out", "w", stdout); ^ user.cpp:23:29: warning: ignoring return value of ‘int scanf(const char*, ...)’, declared with attribute warn_unused_result [-Wunused-result] scanf("%d%d\n", &op, &N); ^ user.cpp:29:26: warning: ignoring return value of ‘char* gets(char*)’, declared with attribute warn_unused_result [-Wunused-result] gets(sir + 1); ^ user.cpp:42:23: 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 /usr/include/c++/4.8/cstdio:42, from /usr/include/i386-linux-gnu/c++/4.8/bits/stdc++.h:46, from user.cpp:1: In function ‘char* gets(char*)’, inlined from ‘int main()’ at user.cpp:42:23: /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/cc6vKOpG.o: In function `main': user.cpp:(.text.startup+0x88): warning: the `gets' function is dangerous and should not be used. user.cpp:(.text.startup+0x2b7): warning: the `gets' function is dangerous and should not be used.