//tree //I t(I n){I d=4;J*p=a(n+1,0),*q;c(p),b(p),q=a(n,0);…
//tree
//I t(I n){I d=4;J*p=a(n+1,0),*q;c(p),b(p),q=a(n,0);for(;d<=n;d+=2){I j=0,m=1;N(n-d+4,m*=2)N(m,j+=c(p=a(d,i+1)),b(p),j+=c(p=a(d,-i-1)),b(p))}R d=c(q),b(q),d;}//O("%d %d\n",2*m,j);
//tree
//I t(I n){I d=4;J*p=a(n+1,0),*q;c(p),b(p),q=a(n,0);for(;d<=n;d+=2){I j=0,m=1;N(n-d+4,m*=2)N(m,j+=c(p=a(d,i+1)),b(p),j+=c(p=a(d,-i-1)),b(p))}R d=c(q),b(q),d;}//O("%d %d\n",2*m,j);