#include <list>
#include <map>
#include <set>
#include <deque>
#include <stack>
#include <queue>
#include <algorithm>
#include <sstream>
#include <iostream>
#include <iomanip>
#include <cstdio>
#include <cmath>
#include <cstdlib>
#include <memory.h>
#include <ctime>
#include <bitset>

using namespace std;

#define ABS(a) ((a>0)?a:-(a))
#define MIN(a,b) ((a<b)?(a):(b))
#define MAX(a,b) ((a<b)?(b):(a))
#define FOR(i,a,n) for (int i=(a);i<(n);++i)
#define FI(i,n) for (int i=0; i<(n); ++i)
#define pnt pair <int, int>
#define mp make_pair
#define PI 3.1415926535897
#define MEMS(a,b) memset(a,b,sizeof(a))
#define LL long long
#define U unsigned

const int N = 300010;
const int M = 100010;
int mod = 1000000007;
LL fact[N];
LL inv[N];
char s1[6];
string s;
int vals[M];
stringstream tmp;
int dp[M][202];
int was[M][202];
int test;

int bp(int val, int p)
{
    if (p == 0)
        return 1;
    LL res = bp(val, p / 2);
    res *= res;
    res %= mod;
    if (p & 1)
    {
        res *= val;
        res %= mod;
    }
    return res;
}
int last;
int r(int n, int k)
{
    if (n == 0)
    {
        if (k > vals[last] + 1)
            return 0;
        return 1;
    }
    if (was[n][k] == test)
        return dp[n][k];
    was[n][k] = test;
    int c = vals[last];
    if ((k == 1) || (k == 2))
    {
        LL res = fact[c + n + n];
        res *= (c + 1);
        res %= mod;
        res *= inv[n];
        res %= mod;
        res *= inv[c + n + 1];
        res %= mod;
        return dp[n][k] = res;
    }
    LL res = r(n, k - 1) - r(n - 1, k - 2);
    if (res < 0)
        res += mod;
    return dp[n][k] = res;
}

int main()
{
#ifdef Fcdkbear
    freopen("in.txt", "r", stdin);
    //freopen("out.txt", "w", stdout);
    double beg = clock();
#endif

    fact[0] = 1;
    FOR(i, 1, N)
    {
        fact[i] = fact[i - 1] * i;
        fact[i] %= mod;
    }
    FOR(i, 0, N)
    {
        inv[i] = bp(fact[i], mod - 2);
    }
    int n;
    scanf("%d", &n);
    MEMS(vals, -1);
    FOR(i, 0, n)
    {
        scanf("%s", s1);
        s = (string)s1;
        if (s[0] == '?')
            continue;
        tmp.clear();
        tmp << s;
        tmp >> vals[i];
    }
    if (vals[0] == -1)
        vals[0] = 0;
    if (vals[0])
    {
        cout << 0 << endl;
        return 0;
    }
    n++;
    vals[n - 1] = 1;
    last = 0;
    LL res = 1;
    FOR(i, 1, n)
    {
        if (vals[i] == 0)
        {
            cout << 0 << endl;
            return 0;
        }
        if (vals[i] != -1)
        {
            test++;
            LL res1 = r(i - last - 1, vals[i]);
            res *= res1;
            res %= mod;
            last = i;
        }
    }
    cout << res << endl;

#ifdef Fcdkbear
    double end = clock();
    fprintf(stderr, "*** Total time = %.3lf ***\n", (end - beg) / CLOCKS_PER_SEC);
#endif
    return 0;
}