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: Runtime Error)


//		HYSO SERIOUS? WHY SO SERIOUS                            RIOUS? WHY SO SERIOUS? WHYSO SERIO
//		 ERIOUS? WHY SO SERIOUS ? WHY                          WHY SO SERIOUS? WHY SOSERIOUSWHYS
//		       OSERIOUS? WHY SO SERIOU         SERIOUS        ERIOUS? WHY SO SERIOUS? WHYS
//		          WHY SO SERIOUS? WHY SOSERIOUS? WHYSOSERIOUS? WHY SO SERIOUS?WHY SO SE
//		           ERIOUS? WHY SO SERIOUS? WHY SO SERIOUS? WHY SO SERIOUS? WHY SOSERIO
//		           WHY SO SERIOUS? WHY SO SERIOUS? WHY SO SERIOUS? WHY SO SERIOUS? WH
//		            SERIOUS?WHYSO SERIOUS? WHY SO SERIOUS? WHY SO SERIOUS? WHYSO SE
//		              ?WHYSOSERIOUS?WHY SO SERIOUS? WHY SO SERIOUS?WHYSO SERIOUS?
//		                           OSERIOUS? WHY SO SERIOUS?WHYSOSER
//		                                 HYSOSERIOUS?WHYSOSERI
//		                                     SOSERIOUS?W
//		                                         SER
//		                                          W


#include 	<ext/pb_ds/assoc_container.hpp> 
#include 	<ext/pb_ds/tree_policy.hpp> 
#include 	<iostream>
#include 	<queue>
#include 	<tuple>
#include 	<vector>
#include	<bits/stdc++.h>
#include	<algorithm>
#include 	<cmath>
#include 	<map>
#include 	<string>
#include 	<iomanip> 
using 		namespace __gnu_pbds; 
using 		namespace std;
#define 	ll  long long int
#define		read(a) long long int a; cin>>a;
#define 	readstr(s) string s; cin>>s;
#define 	readarr(a,l) long long int a[l]={0}; for(ll i=0;i<l;i++) cin>>a[i];
#define 	readc(c) char c; cin>>c;
#define 	loop(i,a,b) for(ll i=a;i<b;i++)
#define 	rloop(i,a,b) for(ll i=a;i>b;i--)
#define 	loopitr(vec) for(auto it=vec.begin();it!=vec.end();it++)
#define 	ff first
#define 	ss second
#define 	readmtrx(i,j,a,b) ll arr[a][b]={0};for(ll i=0;i<a;i++)for(ll j=0;j<b;j++) cin>>arr[i][j];
#define 	v(pi) vector<ll>pi
#define 	all(a) a.begin(), a.end()
#define 	yes cout <<"YES"<<endl;
#define 	no cout <<"NO"<<endl;
#define 	sc(x) cout << (#x) << " is " << (x) << endl;
#define 	vp(pi) vector<pair<ll,ll>>pi
#define 	fast ios_base::sync_with_stdio(false);cin.tie(0);
#define 	pb(p) push_back(p)
#define 	mp make_pair
#define 	mi(lol) map<ll,ll>lol
#define 	fsort(vec) sort(vec.begin(),vec.end())
#define 	rsort(vec) sort(vec.begin(),vec.end(),compare)
#define 	Endl endl
#define 	ordered_set tree<int, null_type,less<int>, rb_tree_tag,tree_order_statistics_node_update> 
#define 	roundoff std::cout << std::setprecision(15)
#define 	inf 9223372036854775807
#define 	infn -9223372036854775807
#define 	pi 3.14159265358979323846
const 		int mod = 1e9+7; 
#define 	REVERSE(vec) reverse(vec.begin(),vec.end())


ll gcd (ll a, ll b) { return b ? gcd (b, a % b) : a; }
ll lcm (ll a, ll b) { return a / gcd(a, b) * b; }

//code start from here 
char ch[1001][1001];
ll sum=0;
ll dp[1001][1001];
ll path(ll i, ll j, ll a,ll b){
	if(dp[i][j]!=-1) return (dp[i][j])%mod;
	if(i==a-1 && j==b-1) return dp[i][j]=1%mod;
	if(i==a-1 && ch[i][j+1]=='#') return dp[i][j]=0;
	if(j==b-1 && ch[i+1][j]=='.' && i+1<=a-1) return dp[i][j]=(path(i+1,j,a,b))%mod;
	if(j==b-1 && ch[i+1][j]=='#') return dp[i][j]=0;
	if(ch[i+1][j]!='#' && ch[i][j+1]!='#' && j+1<=b-1 && i+1<=a-1) return dp[i][j]=(path(i+1,j,a,b)+path(i,j+1,a,b))%mod;
	if(ch[i][j+1]!='#' && ch[i+1][j]!='.' && j+1<=b-1) return dp[i][j]=path(i,j+1,a,b)%mod;
	if(ch[i][j+1]=='#' && ch[i+1][j]=='.' && i+1<=a-1) return dp[i][j]=path(i+1,j,a,b)%mod; 

}

int main() {
	fast;
	#ifndef ONLINE_JUDGE
 	 	freopen("input.txt","r",stdin);
	  	freopen("output.txt","w",stdout);
	#endif
	memset(dp,-1,sizeof(dp));
	read(a)
	read(b)
	loop(j,0,a){
		loop(i,0,b){
			readc(c)
			ch[j][i]=c;
		}
	}
	ll i=0;ll j=0;
	cout<<path(i,j,a,b)<<endl;
	return 0;
}

//ends here