foo.c: In function 'main':
foo.c:42:12: warning: implicit declaration of function 'abs' [-Wimplicit-function-declaration]
    time+=1+abs(a[i-1].di-a[i].di)+abs(a[i-1].dj-a[i].dj);
            ^~~

自豪的采用jd5进行评测(github.com/masnn/jd5)