foo.c: In function 'main':
foo.c:5:21: error: redeclaration of 't' with no linkage
         int n,x,t,i,t;
                     ^
foo.c:5:17: note: previous declaration of 't' was here
         int n,x,t,i,t;
                 ^
foo.c:6:1: warning: ignoring return value of 'scanf', declared with attribute warn_unused_result [-Wunused-result]
 scanf("%d",&n); 
 ^~~~~~~~~~~~~~
foo.c:10:3: warning: ignoring return value of 'scanf', declared with attribute warn_unused_result [-Wunused-result]
   scanf("%d",&a[n]);
   ^~~~~~~~~~~~~~~~~
foo.c:13:2: warning: ignoring return value of 'scanf', declared with attribute warn_unused_result [-Wunused-result]
  scanf("%d",&x);
  ^~~~~~~~~~~~~~

[Hydro](https://hydro.ac)提供评测服务