Compilare: user.c: In function ‘main’: user.c:31:4: warning: implicit declaration of function ‘abs’ [-Wimplicit-function-declaration] sum += max(abs(w.x - v[j].x), abs(w.y - v[j].y)); ^ user.c:19:8: warning: ignoring return value of ‘fscanf’, declared with attribute warn_unused_result [-Wunused-result] fscanf(f_in, "%d %d", &n, &m); ^ user.c:25:9: warning: ignoring return value of ‘fscanf’, declared with attribute warn_unused_result [-Wunused-result] fscanf(f_in, "%d %d", &v[i].x, &v[i].y); ^ user.c:28:9: warning: ignoring return value of ‘fscanf’, declared with attribute warn_unused_result [-Wunused-result] fscanf(f_in, "%d %d", &w.x, &w.y); ^