Compilare: user.c: In function ‘check’: user.c:12:26: warning: unused variable ‘ck’ [-Wunused-variable] int i, k = 0, c = 0, ck = 0; ^ user.c: In function ‘main’: user.c:36:5: warning: implicit declaration of function ‘malloc’ [-Wimplicit-function-declaration] int *N = (int*)malloc((n+1)* sizeof(int)); ^ user.c:36:20: warning: incompatible implicit declaration of built-in function ‘malloc’ [enabled by default] int *N = (int*)malloc((n+1)* sizeof(int)); ^ user.c:46:9: warning: unused variable ‘f’ [-Wunused-variable] int f = 0; ^