Main.cc: In function ‘void exgcd(long long int, long long int, long long int*, long long int*)’:
Main.cc:17:16: error: return-statement with a value, in function returning ‘void’ [-fpermissive]
   17 |         return a;
      |                ^
Main.cc:19:18: error: void value not ignored as it ought to be
   19 |     int ret=exgcd(b,a%b,x,y);
      |             ~~~~~^~~~~~~~~~~
Main.cc:19:9: warning: unused variable ‘ret’ [-Wunused-variable]
   19 |     int ret=exgcd(b,a%b,x,y);
      |         ^~~
Main.cc: In function ‘int main()’:
Main.cc:6:10: warning: ignoring return value of ‘int scanf(const char*, ...)’, declared with attribute warn_unused_result [-Wunused-result]
    6 |     scanf("%lld %lld",&a,&b);
      |     ~~~~~^~~~~~~~~~~~~~~~~~~