Compilare: user.cpp: In function ‘int main()’: user.cpp:45:40: warning: ignoring return value of ‘FILE* freopen(const char*, const char*, FILE*)’, declared with attribute warn_unused_result [-Wunused-result] freopen ("frequent.in", "r", stdin); ^ user.cpp:46:42: warning: ignoring return value of ‘FILE* freopen(const char*, const char*, FILE*)’, declared with attribute warn_unused_result [-Wunused-result] freopen ("frequent.out", "w", stdout); ^ user.cpp:49:23: warning: ignoring return value of ‘int scanf(const char*, ...)’, declared with attribute warn_unused_result [-Wunused-result] scanf ("%d\n", &k); ^ user.cpp:54:39: warning: ignoring return value of ‘char* fgets(char*, int, FILE*)’, declared with attribute warn_unused_result [-Wunused-result] fgets (aux + 1, 400010, stdin); ^ In file included from /usr/include/stdio.h:934:0, from /usr/include/c++/4.8/cstdio:42, from user.cpp:1: In function ‘char* fgets(char*, int, FILE*)’, inlined from ‘int main()’ at user.cpp:54:39: /usr/include/i386-linux-gnu/bits/stdio2.h:253:58: warning: call to ‘__fgets_chk_warn’ declared with attribute warning: fgets called with bigger size than length of destination buffer [enabled by default] return __fgets_chk_warn (__s, __bos (__s), __n, __stream); ^