#include <bits/stdc++.h>
using namespace std;
using ll = long long;
using i64 = long long;
#define pb emplace_back
#define AI(i) begin(i), end(i)
template<class T> bool chmin(T &a, T b) { return b < a && (a = b, true); }
template<class T> bool chmax(T &a, T b) { return a < b && (a = b, true); }
#ifdef KEV
#define DE(args...) kout("[ " + string(#args) + " ] = ", args)
void kout() { cerr << endl; }
template<class T, class ...U> void kout(T a, U ...b) { cerr << a << ' ', kout(b...); }
template<class T> void debug(T l, T r) { while (l != r) cerr << *l << " \n"[next(l)==r], ++l; }
#else
#define DE(...) 0
#define debug(...) 0
#endif

const int MAX_N = 200010, MAX_M = 51, p = 1e9 + 7;

using ap = array<int, MAX_M>;
int n, m;
int c[MAX_N];
ll cnt[MAX_M];
ll w[MAX_N], iw[MAX_N], p2[MAX_N];
ll wb[MAX_N], iwb[MAX_N];
ll pf[MAX_N];
ap lst[MAX_N];

ll inv[MAX_N];
ll g(ll x) {
	return (2 * x * x % p * x % p
		+ 3 * x * x % p
		+ 3 * x + 3) % p;
}
void mul(ll &a, ll b) {
	a = (a * b) % p;
}
void add(ll &a, ll b) {
	a = (a + b) % p;
}
ll bin_pow(ll v, ll t) {
	ll ret = 1;
	for (;t;t>>=1, mul(v, v))
		if (t&1) mul(ret, v);
	return ret;
}

void init() {
	inv[0] = inv[1] = 1;
	p2[0] = 1;
	p2[1] = 2;
	for (int i = 2;i < MAX_N;++i) {
		inv[i] = (p-p/i) * inv[p % i] % p;
		p2[i] = p2[i-1] * 2 % p;
	}
	for (int i = 1;i < MAX_N;++i)
		pf[i] = (pf[i-1] + g(i) * bin_pow(inv[2], i)) % p;
}
ll f(int i) {
	//return 12 * i;
	return 12 * i - 10;
}
ll get_g(ll l, ll r, ll clen) {
	ll ret = 0;
	assert(clen >= r);
	for (int i = l;i <= r;++i) {
		add(ret, p2[clen - i] * f(i));
	}
	return ret;
}

ll cont(ll l, ll r) {
	vector<int> has(m+1);
	for (int i = l;i <= r;++i)
		has[ c[i] ] = true;
	
	vector<int> cnt(m+1);
	for (int i = 1;i+1 < l;++i)
		++cnt[ c[i] ];
	for (int i = r+2;i <= n;++i)
		++cnt[ c[i] ];

	ll ret = g(r - l + 1);
	for (int i = 1;i <= m;++i) {
		if (has[i]) mul(ret, p2[cnt[i]]);
		else mul(ret, p2[cnt[i]] - 1);
	}
	return ret;

}
int main() {
	cin.tie(nullptr)->sync_with_stdio(false);
	init();
	DE(g(1), g(2), g(3), g(2) + g(3) + 2  * g(1));
	cin >> n >> m;
	for (int i = 1;i <= n;++i)
		cin >> c[i];
	for (int i = 1;i <= n;++i) {
		lst[i] = lst[i-1];
		lst[i][c[i]] = i;
		++cnt[c[i]];
	} 
	for (int i = 1;i <= m;++i) {
		w[i] = p2[cnt[i]] - 1;
		iw[i] = bin_pow(w[i], p-2);
		if (cnt[i] > 0)
			wb[i] = p2[cnt[i]-1] - 1;
		else
			wb[i] = 0;
		iwb[i] = bin_pow(wb[i], p-2);
		//DE(i, w[i]);
	}
	ll res = 0;

	for (int r = 1;r <= n;++r) {
		if (r+1 <= n && cnt[ c[r+1] ] == 1) continue;

		int nxt_c = c[r+1];
		if (nxt_c) {
			--cnt[nxt_c];
			swap(w[nxt_c], wb[nxt_c]);
			swap(iw[nxt_c], iwb[nxt_c]);
		}

		ll cur_v = 1;
		for (int i = 1;i <= m;++i) {
			DE(i, cnt[i]);
			//mul(cur_v, p2[ cnt[i] ]-1);
			mul(cur_v, w[i]);
		}

		vector<int> sid(m+1); iota(AI(sid), 0);
		sort(AI(sid), [&](int a, int b) {
				return lst[r][a] > lst[r][b];
				});

		DE(r);
		int clen = 0;
		for (int j = 0;;++j) {
			int p1 = lst[r][ sid[j] ];
			clen += cnt[ sid[j] ];

			DE(clen, sid[j], cnt[ sid[j] ]);

			if (p1 == 0) {
				// len = r
				//ll sc = cur_v;
				ll v = cur_v * g(r) % p * p2[clen-r];
				add(res, v);
				break;
			}

			mul(cur_v, iw[ sid[j] ]);

			if (cnt[ sid[j] ] > 1) {
				clen -= cnt[ sid[j] ];
				ll sc = cur_v; 
				mul(sc, p2[ cnt[sid[j]]-1 ] - 1); 
				int O = r - p1;
				if (O > 0) {
					ll v = sc * g(O) % p * p2[clen - O] % p;
					add(res, v);
				}
				clen += cnt[ sid[j] ];
			}

			int p2 = lst[r][ sid[j+1] ];
			int L = r-p1+1, R = r-p2-1; 
			DE(j, cur_v, L, R, r);

			//upd(L, R, clen, cur_v);

			if (L <= R) {
				ll v = (pf[R] - pf[L-1] + p) % p
					* ::p2[clen - 1] % p; 
				add(res, v * cur_v);
			}

//			for (int j = L;j <= R;++j) {
//				ll v = g(j) * cur_v % p * ::p2[clen - 1 - j] % p;
//
////				int lb = r - j + 1;
////				DE(v, cont(r - j + 1, r), lb, cur_v, g(j), clen - 1 - j);
//				assert(cont(r - j + 1, r) == v);
//				add(res, v);
//			}
			//add(res, get_g(L, R, clen) * cur_v % p * );
		}

		if (nxt_c) {
			++cnt[nxt_c];
			swap(w[nxt_c], wb[nxt_c]);
			swap(iw[nxt_c], iwb[nxt_c]);
		}
	}
	if (res < 0) res += p;
	cout << res << '\n'; 
}