This submission is migrated from previous version of oj.uz, which used different machine for grading. This submission may have different result if resubmitted.
#include <bits/stdc++.h>
#define rep(a, b, c) for (int a = (b); (b) <= (c); a++)
#define per(a, b, c) for (int a = (b); (b) >= (c); a--)
#define nl '\n'
#define ioi exit(0);
const int mod = (int)1e9 + 7;
using namespace std;
void add(int &x, int y) {
x += y;
if (x >= mod) x -= mod;
if (x < 0) x += mod;
}
int sum(int x, int y) {
add(x, y);
return x;
}
int n, m;
int dp[301][301][301];
int calc(int v = 1, int free = m, int must = 0) {
if (v > n) return 1;
if (~dp[v][free][must]) return dp[v][free][must];
int res = calc(v + 1, free, must);
// put < or > or ^
if (free > 0) add(res, calc(v + 1, free - 1, must) * 1ll * free * 3 % mod);
// connect v and ^
if (must > 0) add(res, calc(v + 1, free, must - 1) * 1ll * must % mod);
// open v
if (free > 0) add(res, calc(v + 1, free - 1, must + 1) * 1ll * free % mod);
// connect > and <
if (free > 1) add(res, calc(v + 1, free - 2, must) * 1ll * (free * (free - 1) / 2) % mod);
return dp[v][free][must] = res;
}
int main() {
#ifdef IOI
freopen ("in.txt", "r", stdin);
#endif
cin >> n >> m;
memset(dp, -1, sizeof(dp));
cout << sum(-1, calc()) << nl;
ioi
}
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