foo.c: In function 'main':
foo.c:11:2: warning: this 'if' clause does not guard... [-Wmisleading-indentation]
   11 |  if(j<i)
      |  ^~
foo.c:12:7: note: ...this statement, but the latter is misleadingly indented as if it were guarded by the 'if'
   12 |   r=j;j=i;i=r;
      |       ^
foo.c:5:2: warning: ignoring return value of 'scanf', declared with attribute warn_unused_result [-Wunused-result]
    5 |  scanf("%d%d\n",&b1,&a1);
      |  ^~~~~~~~~~~~~~~~~~~~~~~
foo.c:6:2: warning: ignoring return value of 'scanf', declared with attribute warn_unused_result [-Wunused-result]
    6 |  scanf("%d%d\n",&b2,&a2);
      |  ^~~~~~~~~~~~~~~~~~~~~~~
foo.c:4:22: warning: 'r' may be used uninitialized in this function [-Wmaybe-uninitialized]
    4 |  int a1,a2,b1,b2,m,n,r,j,i;
      |                      ^

[Hydro](https://hydro.ac)提供评测服务