foo.c: In function 'main':
foo.c:9:6: error: 'm' undeclared (first use in this function)
   if(m==2){
      ^
foo.c:9:6: note: each undeclared identifier is reported only once for each function it appears in
foo.c:5:8: warning: variable 'y' set but not used [-Wunused-but-set-variable]
  int x,y,z,l,r=0;
        ^
foo.c:6:2: warning: ignoring return value of 'scanf', declared with attribute warn_unused_result [-Wunused-result]
  scanf("%d %d",&l,&r);
  ^~~~~~~~~~~~~~~~~~~~

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