/in/foo.cc: In function 'int main()':
/in/foo.cc:19:10: error: invalid operands of types 'int' and 'int [1001]' to binary 'operator-'
 b[i]=a[i]-a;
      ~~~~^~
/in/foo.cc:13:7: warning: unused variable 'j' [-Wunused-variable]
 int i,j,m,a[1001]={0},b[1001]={0};
       ^