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| #include <iostream>
#include <cstring>
using namespace std;
int N, K, num[30], ans[30];
bool save[31][31][31][450], got;
void DP(int d, int a, int b, int n);
int main() {
cin >> N >> K;
memset(num, -1, sizeof(num));
memset(ans, -1, sizeof(ans));
DP(0, 0, 0, 0);
if (!got)
cout << -1 << endl;
else {
for (int i = 0; i < N; i++) {
if (ans[i] == 0)
cout << 'A';
else if (ans[i] == 1)
cout << 'B';
else if (ans[i] == 2)
cout << 'C';
}
}
}
void DP(int d, int a, int b, int n) {
if (d == N) {
if (n == K) {
got = true;
memcpy(ans, num, sizeof(num));
}
return;
}
if (save[d][a][b][n])
return;
save[d][a][b][n] = true;
if (got)
return;
num[d] = 0;
DP(d + 1, a + 1, b, n);
if (!got) {
num[d] = 1;
DP(d + 1, a, b + 1, n + a);
}
if (!got) {
num[d] = 2;
DP(d + 1, a, b, n + a + b);
}
num[d] = -1;
}
|
