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

dp = [[-10**18]*(k+1) for i in range(n+1)]
dp[0][0] = p
for i in range(n):
	for j in range(k+1):
		dp[i+1][j] = max(dp[i+1][j], dp[i][j])
	for j in range(k):
		if t[i] == 1:
			dp[i+1][j+1] = max(dp[i+1][j+1], min(10**18+1, dp[i][j] + b[i]))
		else:
			dp[i+1][j+1] = max(dp[i+1][j+1], min(10**18+1, dp[i][j] * 2))
	
if dp[n][k] == 10**18+1:
	print(-1)
else:
	print(dp[n][k])