We are the greatest!

/***************************************************************************/
/* micro-Max, */
/* A chess program smaller than 2KB (of non-blank source), by H.G. Muller */
/***************************************************************************/
/* version 1.6 (1433 non-blank characters) features: */
/* - recursive negamax search */
/* - quiescence search with recaptures */
/* - recapture extensions */
/* - (internal) iterative deepening */
/* - best-move-first ’sorting’ */
/* - full FIDE rules and move-legality checking */

/* accepts under-promotions: type 1,2,3 (=R,B,N) after input move */
/* (input buffer c[] & *P made global, K and N encoding swapped for this) */

#define W while

int M=136,S=128,I=8e3,C=799,Q,O,K,N;

char L,*P,
w[]={0,1,1,-1,3,3,5,9},
o[]={-16,-15,-17,0,1,16,0,1,16,15,17,0,14,18,31,33,0,
7,-1,6,11,8,3,6,
6,4,5,7,3,5,4,6},
b[129],

n[]=".?+knbrq?*?KNBRQ",

c[9];

D(k,q,l,e,E,z,n)
int k,q,l,e,E,z,n;
{
int j,r,m,v,d,h,i,F,G,s;
char t,p,u,x,y,X,Y,H,B;

q–;
d=X=Y=0;

W(d++<n||
z==8&K==I&&(N<1e6&d<98||
(K=X,L=Y&~M,d=2)))
{x=B=X;
h=Y&S;
m=d>1?-I:e;
N++;
do{u=b[x];
if(u&k)
{r=p=u&7;
j=o[p+16];
W(r=p>2&r<0?-r:-o[++j])
{A:
y=x;F=G=S;
do{
H=y=h?Y^h:y+r;
if(y&M)break;
m=E-S&&b[E]&&y-E<2&E-y<2?I:m; /* castling-on-Pawn-check bug fixed */
if(p<3&y==E)H^=16;
t=b[H];if(t&k|p<3&!(y-x&7)-!t)break;
i=99*w[t&7];
m=i<0?I:m; /* castling-on-Pawn-check bug fixed */
if(m>=l)goto C;

if(s=d-(y!=z))
{v=p<6?b[x+8]-b[y+8]:0;
b[G]=b[H]=b[x]=0;b[y]=u|32;
if(!(G&M))b[F]=k+6,v+=30;
if(p<3)
{v-=9*((x-2&M||b[x-2]-u)+
(x+2&M||b[x+2]-u)-1);
if(y+r+1&S)b[y]|=7,i+=C;
}
v=-D(24-k,-l,m>q?-m:-q,-e-v-i,F,y,s);
if(K-I)
{if(v+I&&x==K&y==L&z==8)
{Q=-e-i;O=F;
if(b[y]-u&7&&P-c>5)b[y]-=c[4]&3; /* under-promotions */
return l;
}v=m;
}
b[G]=k+6;b[F]=b[y]=0;b[x]=u;b[H]=t;
if(v>m)
m=v,X=x,Y=y|S&F;
if(h){h=0;goto A;}
}
if(x+r-y|u&32|
p>2&(p-3|j-7||
b[G=x+3^r>>1&7]-k-6
||b[G^1]|b[G^2])
)t+=p<5;
else F=y;
}W(!t);
}}}W((x=x+9&~M)-B);
C:if(m>I-M|m<M-I)d=98;
m=m+I?m:-D(24-k,-I,I,0,S,S,1);
}
return m+=m<e;
}

main()
{
int k=8;

K=8;W(K–)
{b[K]=(b[K+112]=o[K+24]+8)+8;b[K+16]=18;b[K+96]=9;
L=8;W(L–)b[16*L+K+8]=(K-4)*(K-4)+(L-3.5)*(L-3.5);
}

W(1)
{N=-1;W(++N<121)
printf(" %c",N&8&&(N+=7)?10:n[b[N]&15]);
P=c;W((*P++=getchar())>10);
K=I;
if(*c-10)K=*c-16*c[1]+C,L=c[2]-16*c[3]+C;
k^=D(k,-I,I,Q,O,8,2)-I?0:24;
}
}

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