4356f9519040429192097e1904a9b9f55793dc0023a20ae4f3abc59bb2e759a0
// https://szkopul.edu.pl/problemset/problem/LdXEESx2SJmtrU_CkvAXwXNh/site/?key=statement
// OIG III (2 etap)
#include <iostream>
#include <math.h>
constexpr int sizik = 132072;
int v[sizik];
int dp[sizik][21];
int pot2[] = {1, 2, 4, 8, 16, 32, 64, 128, 256, 512, 1024, 2048, 4096, 8192, 16384, 32768, 65536, 131072};
int main() {
std::ios_base::sync_with_stdio(0);
std::cin.tie(0);
std::cout.tie(0);
int n, k;
std::cin >> n >> k;
// k >>= 1;
k /= 2;
int curr = 0;
for (int i = 0; i < n; i++) {
for (int j = 0; j < (1 << i); j++) {
int a, b;
std::cin >> a >> b;
v[++curr] = a + b;
}
}
for (int x = curr; x >= 1; x--) {
dp[x][1] = v[x];
for (int i = 2; i <= k; i++) {
dp[x][i] = dp[x][i - 1];
if (2 * x + 1 >= 131072) {
continue;
}
for (int j = 0; j <= i - 1; j++) {
dp[x][i] = std::max( //
dp[2 * x][j] + dp[2 * x + 1][i - 1 - j] + dp[x][1], //
dp[x][i] //
);
}
}
}
std::cout << std::max(dp[1][k], 0) << '\n';
return 0;
}