foo.cc:3:18: error: array bound is not an integer constant before ']' token
 int n1,n2,n3,a[n1],b[n2],c[n3],d[n1+n2],f[n1+n3],k=0,j=0;
                  ^
foo.cc:3:24: error: array bound is not an integer constant before ']' token
 int n1,n2,n3,a[n1],b[n2],c[n3],d[n1+n2],f[n1+n3],k=0,j=0;
                        ^
foo.cc:3:30: error: array bound is not an integer constant before ']' token
 int n1,n2,n3,a[n1],b[n2],c[n3],d[n1+n2],f[n1+n3],k=0,j=0;
                              ^
foo.cc:3:39: error: array bound is not an integer constant before ']' token
 int n1,n2,n3,a[n1],b[n2],c[n3],d[n1+n2],f[n1+n3],k=0,j=0;
                                       ^
foo.cc:3:48: error: array bound is not an integer constant before ']' token
 int n1,n2,n3,a[n1],b[n2],c[n3],d[n1+n2],f[n1+n3],k=0,j=0;
                                                ^
foo.cc: In function 'int main()':
foo.cc:8:18: error: 'a' was not declared in this scope
      scanf("%d",&a[i]);
                  ^
foo.cc:11:18: error: 'b' was not declared in this scope
      scanf("%d",&b[i]);
                  ^
foo.cc:14:18: error: 'c' was not declared in this scope
      scanf("%d",&c[i]);
                  ^
foo.cc:17:6: error: 'd' was not declared in this scope
      d[k++]=a[i];
      ^
foo.cc:17:13: error: 'a' was not declared in this scope
      d[k++]=a[i];
             ^
foo.cc:20:6: error: 'd' was not declared in this scope
      d[k++]=a[i];
      ^
foo.cc:20:13: error: 'a' was not declared in this scope
      d[k++]=a[i];
             ^
foo.cc:23:6: error: 'f' was not declared in this scope
      f[j++]=a[i];
      ^
foo.cc:23:13: error: 'a' was not declared in this scope
      f[j++]=a[i];
             ^
foo.cc:26:6: error: 'f' was not declared in this scope
      f[j++]=c[i];
      ^
foo.cc:26:13: error: 'c' was not declared in this scope
      f[j++]=c[i];
             ^
foo.cc:28:10: error: 'd' was not declared in this scope
     sort(d,d+k);
          ^
foo.cc:29:10: error: 'f' was not declared in this scope
     sort(f,f+j);
          ^
foo.cc:6:10: warning: ignoring return value of 'int scanf(const char*, ...)', declared with attribute warn_unused_result [-Wunused-result]
     scanf("%d %d %d",&n1,&n2,&n3);
     ~~~~~^~~~~~~~~~~~~~~~~~~~~~~~

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