foo.c: In function 'main':
foo.c:6:11: warning: format '%ld' expects argument of type 'long int *', but argument 2 has type 'int *' [-Wformat=]
  scanf("%ld",&n);
           ^
foo.c:17:7: warning: implicit declaration of function 'abs' [-Wimplicit-function-declaration]
    m+=abs(a[i]-a[j]);
       ^~~

自豪的采用jd5进行评测(github.com/masnn/jd5)