foo.c: In function 'main':
foo.c:11:2: error: unknown type name 'len'; use 'struct' keyword to refer to the type
   11 |  len t;
      |  ^~~
      |  struct 
foo.c:20:6: error: incompatible types when assigning to type 'int' from type 'struct len'
   20 |    t=a[i];
      |      ^
foo.c:22:9: error: incompatible types when assigning to type 'struct len' from type 'int'
   22 |    a[j]=t;
      |         ^
foo.c:10:20: warning: unused variable 'endtree' [-Wunused-variable]
   10 |  int L,M,i,j=0,n=0,endtree=0;
      |                    ^~~~~~~
foo.c:12:2: warning: ignoring return value of 'scanf', declared with attribute warn_unused_result [-Wunused-result]
   12 |  scanf("%d%d",&L,&M);
      |  ^~~~~~~~~~~~~~~~~~~
foo.c:14:3: warning: ignoring return value of 'scanf', declared with attribute warn_unused_result [-Wunused-result]
   14 |   scanf("%d%d",&a[i].beg,&a[i].end);
      |   ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~

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