Compilare: user.c: In function ‘main’: user.c:8:5: warning: implicit declaration of function ‘sqrt’ [-Wimplicit-function-declaration] for (i = 3; i <= sqrt(n); i += 2) ^ user.c:8:22: warning: incompatible implicit declaration of built-in function ‘sqrt’ [enabled by default] for (i = 3; i <= sqrt(n); i += 2) ^ user.c:7:10: warning: ignoring return value of ‘scanf’, declared with attribute warn_unused_result [-Wunused-result] scanf("%d", &n); ^