n,p,k=map(int,input().split())
d=[p]+[-1<<60]*k
for i in range(n):
    t,b=map(int,input().split())
    if t==1:
        for j in range(k,0,-1):d[j]=max(d[j],d[j-1]+b)
    else:
        for j in range(k,0,-1):d[j]=max(d[j],d[j-1]*2)
print(-1 if d[k]>10**18 else d[k])