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OI-codes/LibreOJ/10170/10170.cpp

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#include <iostream>
#include <vector>
using std::cin;
using std::cout;
const char endl = '\n';
int n, k;
int cnt, r[2005], s[2005];
long long f[15][2005][105], ans;
void dfs(int x, int sum, int len) {
if (len >= n) {
r[++cnt] = x;
s[cnt] = sum;
return;
}
dfs(x, sum, len + 1);
dfs(x + (1 << len), sum + 1, len + 2);
}
int main() {
std::ios::sync_with_stdio(false);
cin >> n >> k;
dfs(0, 0, 0);
for (int i = 1; i <= cnt; i++) f[1][i][s[i]] = 1;
for (int i = 2; i <= n; i++) {
for (int j = 1; j <= cnt; j++) {
for (int p = 1; p <= cnt; p++) {
if ((r[j] & r[p]) || ((r[j] << 1) & r[p]) || (r[j] & (r[p] << 1))) continue;
for (int l = k; l >= s[j]; l--) {
f[i][j][l] += f[i - 1][p][l - s[j]];
}
}
}
}
for (int i = 1; i <= cnt; i++) ans += f[n][i][k];
cout << ans << endl;
return 0;
}