n,p,k = list(map(int, input().split(' ')))
dp = [[p] * (k+1) for i in range(n+1)]
for i in range(n):
    t,b = list(map(int, input().split(' ')))
    for j in range(k+1):
        dp[i+1][j] = max(dp[i+1][j],dp[i][j])
        if j + 1 <= k:
            if t == 1:
                dp[i+1][j+1] = max(dp[i+1][j+1],dp[i][j] + b)
            else:
                dp[i+1][j+1] = max(dp[i+1][j+1],dp[i][j]*2)
if dp[n][k] > 1e18:
    print(-1)
else:
    print(dp[n][k])