N,P,K=map(int,input().split())
L1=[]
L2=[]
for i in range(N):
  t,b=map(int,input().split())
  if t==1:
    L1.append(b)
  else:
    L2.append(2)
L1.sort(reverse=True)
L2.sort(reverse=True)
u=[1]
for i in range(len(L2)):
  u.append(L2[i])
result=0
for j in range(1,K+1):
  if j>=len(u):
    break
  u[j]=u[j-1]*u[j]
  if u[j]>10**18:
    print(-1)
    exit()
result=0
for i in range(len(L1)):
  if i>0:
    P+=L1[i-1]
  rest=K-i
  if rest<0:
    break
  if rest<len(u):
    score=P*u[rest]
  else:
    score=P*u[-1]
  result=max(result,score)
if result<=10**18:
  print(result)
else:
  print(-1)