n,p,k=map(int,input().split())
ans=[-10**18]*(k+1)
ans[0]=p
for i in range(n):
    ans2=[-10**18]*(k+1)
    for j in range(k+1):
        ans2[j]=ans[j]
    t,b=map(int,input().split())
    if t==1:
        for j in range(1,k+1):
            ans2[j]=max(ans2[j],ans[j-1]+b)
    else:
        for j in range(1,k+1):
            ans2[j]=max(ans2[j],2*ans[j-1])
    ans=ans2
    if ans[k]>10**18:
        print(-1)
        exit()
print(ans[k])