foo.cc: In function 'void df(int)':
foo.cc:8:11: warning: unused variable 't' [-Wunused-variable]
     int i,t,q;
           ^
foo.cc: In function 'int main()':
foo.cc:24:18: warning: ignoring return value of 'int scanf(const char*, ...)', declared with attribute warn_unused_result [-Wunused-result]
             scanf("%d",&a[i]);
             ~~~~~^~~~~~~~~~~~