View Compilation Error

0_0_39502743_19405.cpp: In function 'long long int merge(long long int, long long int, long long int, long long int, long long int&)':
0_0_39502743_19405.cpp:25:9: error: return-statement with no value, in function returning 'long long int' [-fpermissive]
   25 |         return;
      |         ^~~~~~