Compilare: user.c: In function ‘main’: user.c:12:2: warning: implicit declaration of function ‘scanf’ [-Wimplicit-function-declaration] scanf("%d",&n); ^ user.c:12:2: warning: incompatible implicit declaration of built-in function ‘scanf’ [enabled by default] user.c:16:3: warning: implicit declaration of function ‘printf’ [-Wimplicit-function-declaration] printf("%d\n",gcd(a,b)); ^ user.c:16:3: warning: incompatible implicit declaration of built-in function ‘printf’ [enabled by default]