Compilare: main.cpp: In function 'int main()': main.cpp:27:17: warning: variable 'uf' set but not used [-Wunused-but-set-variable] int n , c , uf , ub , i , x , y , ult , q , val; ^~ main.cpp:29:32: warning: ignoring return value of 'int fscanf(FILE*, const char*, ...)', declared with attribute warn_unused_result [-Wunused-result] fscanf (fin,"%d%d\n",&n,&c); ^ main.cpp:31:31: warning: ignoring return value of 'char* fgets(char*, int, FILE*)', declared with attribute warn_unused_result [-Wunused-result] fgets (v + 1 , DIMN , fin); ^ main.cpp:48:38: 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 , 20000000 , fin); ^ 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:1: In function 'char* fgets(char*, int, FILE*)', inlined from 'int main()' at main.cpp:31:31: /usr/include/x86_64-linux-gnu/bits/stdio2.h:261:58: warning: call to '__fgets_chk_warn' declared with attribute warning: fgets called with bigger size than length of destination buffer return __fgets_chk_warn (__s, __bos (__s), __n, __stream); ^