Compilare: main.cpp: In function 'int main()': main.cpp:50:9: warning: unused variable 'dr' [-Wunused-variable] int dr=0; ^~ main.cpp:30:31: warning: ignoring return value of 'FILE* freopen(const char*, const char*, FILE*)', declared with attribute warn_unused_result [-Wunused-result] freopen("nc.in","r",stdin); ^ main.cpp:31:33: warning: ignoring return value of 'FILE* freopen(const char*, const char*, FILE*)', declared with attribute warn_unused_result [-Wunused-result] freopen("nc.out","w",stdout); ^ main.cpp:34:29: warning: ignoring return value of 'size_t fread(void*, size_t, size_t, FILE*)', declared with attribute warn_unused_result [-Wunused-result] fread(s,1,4000000,stdin); ^ In file included from /usr/include/stdio.h:936:0, from /usr/include/c++/6/cstdio:42, from /usr/include/x86_64-linux-gnu/c++/6/bits/stdc++.h:46, from main.cpp:2: In function 'size_t fread(void*, size_t, size_t, FILE*)', inlined from 'int main()' at main.cpp:34:29: /usr/include/x86_64-linux-gnu/bits/stdio2.h:293:71: warning: call to '__fread_chk_warn' declared with attribute warning: fread called with bigger size * nmemb than length of destination buffer return __fread_chk_warn (__ptr, __bos0 (__ptr), __size, __n, __stream); ^