add function for declaring an interactive tasks

include/soi

@@ -74,11 +74,17 @@ soi_initializer soi_initializer_{true};
 soi_initializer soi_initializer_{false};
 #endif
 
+void interactive_task() {
+  std::cin.tie(&std::cout);
+}
+
 } // end namespace soi
 
 #include "bits/soi-io.hpp"
 #include "bits/soi-redirect.hpp"
 #include "bits/soi-deprecate.hpp"
 
+using soi::interactive_task;
+
 #define int int64_t
 using namespace std;