Compilare: user.cpp: In function ‘int main()’: user.cpp:22:34: warning: ignoring return value of ‘FILE* freopen(const char*, const char*, FILE*)’, declared with attribute warn_unused_result [-Wunused-result] freopen("cobai.in","r",stdin); ^ user.cpp:23:36: warning: ignoring return value of ‘FILE* freopen(const char*, const char*, FILE*)’, declared with attribute warn_unused_result [-Wunused-result] freopen("cobai.out","w",stdout); ^ user.cpp:25:27: warning: ignoring return value of ‘int scanf(const char*, ...)’, declared with attribute warn_unused_result [-Wunused-result] scanf("%d %d\n",&n,&m); ^ user.cpp:26:38: warning: ignoring return value of ‘size_t fread(void*, size_t, size_t, FILE*)’, declared with attribute warn_unused_result [-Wunused-result] fread(buff,1,NMAX*NMAX+NRS,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 ‘size_t fread(void*, size_t, size_t, FILE*)’, inlined from ‘int main()’ at user.cpp:26:38: /usr/include/i386-linux-gnu/bits/stdio2.h:285:71: warning: call to ‘__fread_chk_warn’ declared with attribute warning: fread called with bigger size * nmemb than length of destination buffer [enabled by default] return __fread_chk_warn (__ptr, __bos0 (__ptr), __size, __n, __stream); ^