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)


// Problem : H - Grid 1
// Contest : AtCoder - Educational DP Contest
// URL : https://atcoder.jp/contests/dp/tasks/dp_h
// Memory Limit : 1024 MB
// Time Limit : 2000 ms
// Powered by CP Editor (https://github.com/cpeditor/cpeditor)

#include<bits/stdc++.h>
using namespace std;

#define ff first
#define fs second
#define lb lower_bound
#define ub upper_bound

#define int long long
#define pii pair<int, int>
#define vi vector<int>
#define vvi vector< vi >
#define vpii vector< pii >
#define vb vector<bool>
#define si set<int>
#define mii map<int, int>
#define mci map<char, int>
#define md 1000000007
#define pb push_back
#define eb emplace_back
#define fio ios_base::sync_with_stdio (false); cin.tie (NULL);  cout.tie (NULL);
#define qw1(x) cerr<<#x<<": "<<x<<" "<<endl
#define qw2(x, y) cerr<<#x<<": "<<x<<" | "<<#y<<": "<<y<<endl
#define qw3(x, y, z) cerr<<#x<<":" <<x<<" | "<<#y<<": "<<y<<" | "<<#z<<": "<<z<<endl
#define qw4(a, b, c, d) cerr<<#a<<": "<<a<<" | "<<#b<<": "<<b<<" | "<<#c<<": "<<c<<" | "<<#d<<": "<<d<<endl


#define f(i,a,b) for(int i=(int)a;i<=(int)b;i++)
#define rl(i,a,b) for(int i=(int)a;i>=(int)b;i--)
#define all(x) x.begin(),x.end()
#define endl '\n'
void printv(vector<int>  v){ for(int i=0;i<v.size();i++) cout<<v[i]<<' '; cout<<endl;   }
int bem(int m , int n, int mod) { int res=1; while(n){
	     			        if(n%2!=0) { res*=m; res%=mod; }
	    			        m*=m;   m%=mod;   n/=2;
			                          }
				return res;	}
int be(int a, int b) { int res=1; 	while(b){
				if(b%2!=0) res*=a;
				a*=a; b/=2;
				}
			return res;	}
void sieve(int n, vb &prime){
    prime[0]=false;     prime[1]=false;
    for(int i=2;i*i<=n;i++){
         if(prime[i]==true){
              for(int j=i*i;j<=n;j+=i)    prime[j]=false;
             	  }
    	 }
	}
vvi dp;
void solve()
  {
int h, w; cin>>h>>w;
vector<string> v(h);
f(i, 0, h-1) cin>>v[i];
// f(i, 0, h-1) cout<<v[i]<<endl;
dp.resize(h+1, vi (w+1, 0));
f(i, 2, w) {
	if(v[0][i-1]=='#') { break; }
	else dp[1][i]=1;
	// qw2(i, dp[1][i]);
	// f(i,1,h) {f(j,1,w) cout<<dp[i][j]<<' '; cout<<endl;}
	
}
//f(i,1,h) {f(j,1,w) cout<<dp[i][j]<<' '; cout<<endl;}
f(i, 2, h) {
	if(v[i-1][0]=='#') { break; }
	else dp[i][1]=1;
}
// f(i,1,h) {f(j,1,w) cout<<dp[i][j]<<' '; cout<<endl;}
f(i, 2, h)
	f(j, 2, w)
	{
		if(v[i-2][j-1]=='#' && v[i-1][j-2]=='#')
			continue;
		else if(v[i-2][j-1]=='#')
		dp[i][j]=(dp[i][j-1])%md;
		else if(v[i-1][j-2]=='#')
		dp[i][j]=(dp[i-1][j])%md;
		else
		dp[i][j]=(dp[i-1][j]+dp[i][j-1] + md) % md;		
	}
// f(i,1,h) {f(j,1,w) cout<<dp[i][j]<<' '; cout<<endl;}
cout<<(dp[h][w]) % md<<endl;

  }

int32_t main ()
{
//fio
int t=1; 
//cin>>t; 
while(t--){
	solve();
}
 
}