n, p, k = map(int, input().split())
t = [0 for i in range(n)]
b = [0 for i in range(n)]
for i in range(n):
    t[i], b[i] = map(int, input().split())


# i個目までのアイテムをj個装備した時の攻撃力のdp
dp = [[0 for i in range(k+1)] for j in range(n+1)]
# dpの左上
dp[0][0]=p
for i in range(1, n+1):
    for j in range(k+1):
        dp[i][j]=max(dp[i][j],dp[i-1][j])
    
    for j in range(k):
        if j+1<=k:
            if t[i-1]==1:
                dp[i][j+1]=max(dp[i][j+1],dp[i-1][j]+b[i-1])
            else:
                dp[i][j+1]=max(dp[i][j+1],dp[i-1][j]*2)
            if dp[i][k]>10**18:
                print(-1)
                exit()

print(dp[n][k])