Problem:
Score : 100 points

Problem Statement

There is a grid with H horizontal rows and W vertical columns.
Let (i, j) denote the square at the i-th row from the top and the j-th column from the left.

For each i and j (1 \leq i \leq H, 1 \leq j \leq W), Square (i, j) is described by a character a_{i, j}.
If a_{i, j} is ., Square (i, j) is an empty square; if a_{i, j} is #, Square (i, j) is a wall square.
It is guaranteed that Squares (1, 1) and (H, W) are empty squares.

Taro will start from Square (1, 1) and reach (H, W) by repeatedly moving right or down to an adjacent empty square.

Find the number of Taro's paths from Square (1, 1) to (H, W).
As the answer can be extremely large, find the count modulo 10^9 + 7.

Constraints

H and W are integers.

2 \leq H, W \leq 1000

a_{i, j} is . or #.

Squares (1, 1) and (H, W) are empty squares.

Input

Input is given from Standard Input in the following format:

H W
a_{1, 1}\ldotsa_{1, W}
:
a_{H, 1}\ldotsa_{H, W}

Output

Print the number of Taro's paths from Square (1, 1) to (H, W), modulo 10^9 + 7.

Sample Input 1

3 4
...#
.#..
....

Sample Output 1

3

There are three paths as follows:

Sample Input 2

5 2
..
#.
..
.#
..

Sample Output 2

0

There may be no paths.

Sample Input 3

5 5
..#..
.....
#...#
.....
..#..

Sample Output 3

24

Sample Input 4

20 20
....................
....................
....................
....................
....................
....................
....................
....................
....................
....................
....................
....................
....................
....................
....................
....................
....................
....................
....................
....................

Sample Output 4

345263555

Be sure to print the count modulo 10^9 + 7.

Solution in C++14 (GCC 5.4.1) (judge verdict: Accepted)

#include <bits/stdc++.h>
//For ordered_set
#include <ext/pb_ds/assoc_container.hpp>
#include <ext/pb_ds/tree_policy.hpp>
#define MOD 1000000007
#define test int t; cin>>t; while(t--)
#define init(arr,val) memset(arr,val,sizeof(arr))
#define loop(i,a,b) for(int i=a;i<b;i++)
#define loopr(i,a,b) for(int i=a;i>=b;i--)
#define loops(i,a,b,step) for(int i=a;i<b;i+=step)
#define looprs(i,a,b,step) for(int i=a;i>=b;i-=step)
#define ull unsigned long long int
#define ll long long int
#define P pair
#define PLL pair<long long, long long>
#define PII pair<int, int>
#define PUU pair<unsigned long long int, unsigned long long int>
#define L list
#define V vector
#define D deque
#define ST set
#define MS multiset
#define M map
#define UM unordered_map
#define mp make_pair
#define pb push_back
#define pf push_front
#define MM multimap
#define F first
#define S second
#define IT iterator
#define RIT reverse_iterator
#define FAST ios_base::sync_with_stdio(false);cin.tie();cout.tie();
#define FILE_READ_IN freopen("input.txt","r",stdin);
#define FILE_READ_OUT freopen("output.txt","w",stdout);
#define all(a) a.begin(),a.end()
#define ld long double
using namespace std;
// For ordered_set
using namespace __gnu_pbds;
template <typename T>
using ord_set = tree<T,null_type,less<T>,rb_tree_tag,tree_order_statistics_node_update>;
const ll maxn = 1e5;
const ll inf = 1e9;
const double pi = acos(-1);
char A[1001][1001];
ll cache[1001][1001];
int main(){
    FAST
    init(cache,0);
    ll h,w;
    cin>>h>>w;
    loop(i,0,h){
        loop(j,0,w){
            cin>>A[i][j];
        }
    }
    // ll ans = 0;
    cache[h][w] = 1;
    loopr(i,h+1,1){
        loopr(j,w+1,1){
            if(i==h+1 && j==w+1){
                continue;
            }
            if(i<=h){
                if(A[i][j-1]=='.'){
                    cache[i][j] = cache[i][j] + cache[i+1][j]%MOD;
                }
            }
            if(j<=w){
                if(A[i-1][j]=='.'){
                    cache[i][j] = (cache[i][j]%MOD + cache[i][j+1]%MOD)%MOD;
                }
            }
        }
    }
    // loop(i,1,h+1){
    //     loop(j,1,w+1){
    //         cout<<cache[i][j]<<" ";
    //     }
    //     cout<<"\n";
    // }
    ll ans = cache[1][1]%MOD;
    cout<<ans<<endl;
   return 0;
}