Compilare: user.c: In function ‘main’: user.c:17:1: warning: implicit declaration of function ‘sqrt’ [-Wimplicit-function-declaration] sqrtN = (int)sqrt((double)copyOfN); ^ user.c:17:14: warning: incompatible implicit declaration of built-in function ‘sqrt’ [enabled by default] sqrtN = (int)sqrt((double)copyOfN); ^ user.c:8:7: warning: variable ‘file1’ set but not used [-Wunused-but-set-variable] FILE *file1, *file2; ^