ll@n; ll a[n][n]; ll x=0,y=0,e=0; rep(i,n*n){ a[y][x]=i+1; if(i&1){ if(x==y){ x=y=n-y; }else{ swap(x,y); } }else{ e^=x+y!=n-1; (e?y:x)+=1; } } wt(a(n,n));