/in/foo.c:2:1: warning: return type defaults to 'int' [-Wimplicit-int]
 Output(int a[], int n)
 ^~~~~~
/in/foo.c: In function 'Output':
/in/foo.c:9:1: warning: control reaches end of non-void function [-Wreturn-type]
 }
 ^
/in/foo.c: In function 'MergeSubs':
/in/foo.c:54:9: warning: 'm' may be used uninitialized in this function [-Wmaybe-uninitialized]
         Merge(c, l,m,n-1);
         ^~~~~~~~~~~~~~~~~