View Compilation Error

0_0_39811357_12484.cpp: In function 'void exgcd(__int128, __int128, __int128&, __int128&)':
0_0_39811357_12484.cpp:21:24: error: return-statement with a value, in function returning 'void' [-fpermissive]
   21 |                 return a;
      |                        ^
0_0_39811357_12484.cpp:23:19: error: void value not ignored as it ought to be
   23 |         ll d=exgcd(b,a%b,y,x);
      |              ~~~~~^~~~~~~~~~~