feat: complex result

a.cc

@@ -1,8 +1,13 @@
 #include <iostream>
+#include <string>
 
 int main(int argc, char *argv[]) {
-  std::string str;
-  std::cin >> str;
+  std::string str, line;
+
+  while (std::getline(std::cin, line)) {
+    str += line + "\n";
+  }
+
   std::cout << str;
   return 0;
 }

cases/empty.in

@@ -1 +0,0 @@
-

cases/empty.out

@@ -1 +0,0 @@
-