foo.cc: In function 'int main()':
foo.cc:4:33: warning: unused variable 't' [-Wunused-variable]
     int n,i,a[10000],j,flag=0,k,t,num=0;
                                 ^
foo.cc:5:7: warning: ignoring return value of 'int scanf(const char*, ...)', declared with attribute warn_unused_result [-Wunused-result]
  scanf("%d",&n);
  ~~~~~^~~~~~~~~
foo.cc:8:8: warning: ignoring return value of 'int scanf(const char*, ...)', declared with attribute warn_unused_result [-Wunused-result]
   scanf("%d",&a[i]);
   ~~~~~^~~~~~~~~~~~