n, P, K = map(int, input().split())
data = [list(map(int, input().split())) for _ in range(n)]
pair = []

# 組み合わせ生成（0-indexに修正）
def dfs(start, path):
    if len(path) == K:
        pair.append(path)
        return
    for i in range(start, n):
        dfs(i+1, path + [i])

dfs(0, [])

# アイテム処理（return追加）
def item(power, t, b):
    if not (0 < power < 10**18):
        return -1

    if t == 1:
        power += b
    elif t == 2:
        power *= 2
        if power > 10**18:
            return -1

    return power

# 計算
for comb in pair:
    power = P
    for idx in comb:
        power = item(power, data[idx][0], data[idx][1])
        if power == -1:
            break

print(power)