import sys
input = sys.stdin.readline

N,P,K=map(int,input().split())

DP=[0]*(K+1)
DP[0]=P


for i in range(N):
    t,b=map(int,input().split())

    for j in range(K-1,-1,-1):
        if t==1:
            DP[j+1]=max(DP[j+1],DP[j]+b)
        else:
            DP[j+1]=max(DP[j+1],DP[j]*2)

if DP[-1]>10**18:
    print(-1)
else:
    print(DP[-1])