foo.c: In function 'main':
foo.c:13:12: warning: unused variable 'd' [-Wunused-variable]
   13 |  int a,b,c,d,t,sum;
      |            ^
foo.c:13:10: warning: unused variable 'c' [-Wunused-variable]
   13 |  int a,b,c,d,t,sum;
      |          ^
foo.c:14:2: warning: ignoring return value of 'scanf', declared with attribute warn_unused_result [-Wunused-result]
   14 |  scanf("%d%d",&a,&b);
      |  ^~~~~~~~~~~~~~~~~~~

[Hydro](https://hydro.ac)提供评测服务