u=0
u,cols,basis,x,pi=runnode(cols,basis,0,0,0,u)
roots=[c for c in cols if c['kind']=='m']
vals={c['cid']:x[k] for k,c in enumerate(basis)}
def yy(i,j): return sum(vals.get(c['cid'],F(0)) for c in roots if c['pair']==(i,j))
print('ROOT y',[(p,yy(p[0],p[1])) for p in P])
print('ROOT obj',sum(c['cost']*x[k] for k,c in enumerate(basis)))
cand=[]
for (i,j) in P:
 q=yy(i,j)
 if q>0 and q<1: cand.append((abs(q-F(1,2)),i,j))
print('CAND',cand)
_,a,b=min(cand)
print('BRANCH',a,b)