foo.c: In function 'main':
foo.c:10:2: error: 'd0' undeclared (first use in this function)
   10 |  d0
      |  ^~
foo.c:10:2: note: each undeclared identifier is reported only once for each function it appears in
foo.c:10:4: error: expected ';' before '{' token
   10 |  d0
      |    ^
      |    ;
   11 |  {
      |  ~  
foo.c:4:27: warning: unused variable 'i' [-Wunused-variable]
    4 |     int b1,a1,b2,a2,x1,x2,i,j,k;
      |                           ^
foo.c:5:2: warning: ignoring return value of 'scanf', declared with attribute warn_unused_result [-Wunused-result]
    5 |  scanf("%d%d\n%d%d\n",&b1,&a1,&b2,&a2);
      |  ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~

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