Compilare: In file included from main.c:1:0: main.c: In function 'read': main.c:6:17: warning: implicit declaration of function 'getchar_unlocked' [-Wimplicit-function-declaration] #define getchar getchar_unlocked ^ main.c:12:24: note: in expansion of macro 'getchar' while (!isdigit(ch=getchar())); ^~~~~~~ main.c: In function '_union': main.c:33:8: warning: suggest explicit braces to avoid ambiguous 'else' [-Wparentheses] if (x!=y) ^ main.c: In function 'main': main.c:48:9: warning: variable 'n' set but not used [-Wunused-but-set-variable] int n, m; ^ main.c:45:5: warning: ignoring return value of 'freopen', declared with attribute warn_unused_result [-Wunused-result] freopen("disjoint.in", "r", stdin); ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ main.c:46:5: warning: ignoring return value of 'freopen', declared with attribute warn_unused_result [-Wunused-result] freopen("disjoint.out", "w", stdout); ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~