N,P,K=map(int,input().split())
counttwo=0
ones=[]
dat=[]
for _ in range(N):
    t,b=map(int,input().split())
    if t==2:
        counttwo+=1
    else:
        ones.append(b)
    dat.append([t,b])
ones.sort(reverse=True)
ans=0
for i in range(min(counttwo+1,K)):
    use=K-i
    if len(ones)>=use:
        lis=[]
        mul=1
        twocount=0
        count=0
        for j in range(N-1,-1,-1):
            if dat[j][0]==2:
                if twocount<i:
                    mul*=2
                    twocount+=1
            else:
                lis.append(mul*dat[j][1])
        lis.sort(reverse=True)
        tmp=P*mul+sum(lis[:use])
        if tmp>=10**18:
            print(-1)
            exit(0)
        ans=max(ans,tmp)
print(ans)