# 2次元dp、dp[i番目まで見て][j個使ったときの]最高値

N, P, K = map(int, input().split())
TB = []
for i in range(N):
    t, b = map(int, input().split())
    TB.append((t, b))

dp = [[0]*(K+1) for i in range(N+1)]
dp[0][0] = P

for i in range(1, N+1):
    t, b = TB[i-1]
    # 使わない
    for j in range(K+1):
        dp[i][j] = max(dp[i][j], dp[i-1][j])
    # 使う
    for j in range(K+1):
        if t == 1:
            if j+1<=K:
                dp[i][j+1] = max(dp[i][j+1], dp[i-1][j]+b)
                if dp[i][j+1] > 10**18:
                    print(-1)
                    exit()
        elif t == 2:
            if j+1<=K:
                dp[i][j+1] = max(dp[i][j+1], dp[i-1][j]*2)
                if dp[i][j+1] > 10**18:
                    print(-1)
                    exit()
    #print(dp[i])
    
ans = dp[N][K]
print(ans)