Language: C

a;f(H,W){for(long long i=H,x,y,z,t;i--;a=t<?a)x=(H-i)*W,y=W/2*i,z=(W+1)/2*i,t=x>z?x-y:x<y?z-x:i;}main(H,W){scanf("%d%d",&H,&W);printf("%d\n",H*W%3?a=H<?W,f(H,W),f(W,H),a:0);}

Compiler output:
main.c:1:1: warning: data definition has no type or storage class
    1 | a;f(H,W){for(long long i=H,x,y,z,t;i--;a=t<?a)x=(H-i)*W,y=W/2*i,z=(W+1)/2*i,t=x>z?x-y:x<y?z-x:i;}main(H,W){scanf("%d%d",&H,&W);printf("%d\n",H*W%3?a=H<?W,f(H,W),f(W,H),a:0);}
      | ^
main.c:1:1: error: type defaults to 'int' in declaration of 'a' [-Wimplicit-int]
main.c:1:3: error: return type defaults to 'int' [-Wimplicit-int]
    1 | a;f(H,W){for(long long i=H,x,y,z,t;i--;a=t<?a)x=(H-i)*W,y=W/2*i,z=(W+1)/2*i,t=x>z?x-y:x<y?z-x:i;}main(H,W){scanf("%d%d",&H,&W);printf("%d\n",H*W%3?a=H<?W,f(H,W),f(W,H),a:0);}
      |   ^
main.c: In function 'f':
main.c:1:3: error: type of 'H' defaults to 'int' [-Wimplicit-int]
main.c:1:3: error: type of 'W' defaults to 'int' [-Wimplicit-int]
main.c:1:44: error: expected expression before '?' token
    1 | a;f(H,W){for(long long i=H,x,y,z,t;i--;a=t<?a)x=(H-i)*W,y=W/2*i,z=(W+1)/2*i,t=x>z?x-y:x<y?z-x:i;}main(H,W){scanf("%d%d",&H,&W);printf("%d\n",H*W%3?a=H<?W,f(H,W),f(W,H),a:0);}
      |                                            ^
main.c: At top level:
main.c:1:98: error: return type defaults to 'int' [-Wimplicit-int]
    1 | a;f(H,W){for(long long i=H,x,y,z,t;i--;a=t<?a)x=(H-i)*W,y=W/2*i,z=(W+1)/2*i,t=x>z?x-y:x<y?z-x:i;}main(H,W){scanf("%d%d",&H,&W);printf("%d\n",H*W%3?a=H<?W,f(H,W),f(W,H),a:0);}
      |                                                                                                  ^~~~
main.c: In function 'main':
main.c:1:98: error: type of 'H' defaults to 'int' [-Wimplicit-int]
main.c:1:98: error: type of 'W' defaults to 'int' [-Wimplicit-int]
main.c:1:108: error: implicit declaration of function 'scanf' [-Wimplicit-function-declaration]
    1 | a;f(H,W){for(long long i=H,x,y,z,t;i--;a=t<?a)x=(H-i)*W,y=W/2*i,z=(W+1)/2*i,t=x>z?x-y:x<y?z-x:i;}main(H,W){scanf("%d%d",&H,&W);printf("%d\n",H*W%3?a=H<?W,f(H,W),f(W,H),a:0);}
      |                                                                                                            ^~~~~
main.c:1:1: note: include '<stdio.h>' or provide a declaration of 'scanf'
  +++ |+#include <stdio.h>
    1 | a;f(H,W){for(long long i=H,x,y,z,t;i--;a=t<?a)x=(H-i)*W,y=W/2*i,z=(W+1)/2*i,t=x>z?x-y:x<y?z-x:i;}main(H,W){scanf("%d%d",&H,&W);printf("%d\n",H*W%3?a=H<?W,f(H,W),f(W,H),a:0);}
main.c:1:108: warning: incompatible implicit declaration of built-in function 'scanf' [-Wbuiltin-declaration-mismatch]
    1 | a;f(H,W){for(long long i=H,x,y,z,t;i--;a=t<?a)x=(H-i)*W,y=W/2*i,z=(W+1)/2*i,t=x>z?x-y:x<y?z-x:i;}main(H,W){scanf("%d%d",&H,&W);printf("%d\n",H*W%3?a=H<?W,f(H,W),f(W,H),a:0);}
      |                                                                                                            ^~~~~
main.c:1:108: note: include '<stdio.h>' or provide a declaration of 'scanf'
main.c:1:128: error: implicit declaration of function 'printf' [-Wimplicit-function-declaration]
    1 | a;f(H,W){for(long long i=H,x,y,z,t;i--;a=t<?a)x=(H-i)*W,y=W/2*i,z=(W+1)/2*i,t=x>z?x-y:x<y?z-x:i;}main(H,W){scanf("%d%d",&H,&W);printf("%d\n",H*W%3?a=H<?W,f(H,W),f(W,H),a:0);}
      |                                                                                                                                ^~~~~~
main.c:1:128: note: include '<stdio.h>' or provide a declaration of 'printf'
main.c:1:128: warning: incompatible implicit declaration of built-in function 'printf' [-Wbuiltin-declaration-mismatch]
main.c:1:128: note: include '<stdio.h>' or provide a declaration of 'printf'
main.c:1:152: error: expected expression before '?' token
    1 | a;f(H,W){for(long long i=H,x,y,z,t;i--;a=t<?a)x=(H-i)*W,y=W/2*i,z=(W+1)/2*i,t=x>z?x-y:x<y?z-x:i;}main(H,W){scanf("%d%d",&H,&W);printf("%d\n",H*W%3?a=H<?W,f(H,W),f(W,H),a:0);}
      |                                                                                                                                                        ^