Compilare: user.c: In function ‘calc’: user.c:20:13: warning: implicit declaration of function ‘abs’ [-Wimplicit-function-declaration] s=(s%4001+calc(i-1,abs(r-v[k]%3)%3)%4001)%4001; ^ user.c: In function ‘main’: user.c:33:11: warning: ignoring return value of ‘fscanf’, declared with attribute warn_unused_result [-Wunused-result] fscanf(fi,"%d%d",&n,&k); ^ user.c:35:15: warning: ignoring return value of ‘fscanf’, declared with attribute warn_unused_result [-Wunused-result] fscanf(fi,"%d",&v[i]); ^