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)

/********************************
* AUTHOR:  ARNAB SEN             *
* NICK  :  arnab1729             *
* INSTITUTION: IIEST, SHIBPUR    *
********************************/

#include<bits/stdc++.h>

using namespace std;

typedef string                         STR;
typedef long long                      LL;
typedef long double                    LD;
typedef unsigned long long             ULL;
typedef vector<int>                    VI;
typedef priority_queue<int>            PQI;
typedef vector<LL>                     VLL;
typedef vector<ULL>                    VULL;
typedef vector<STR>                    VS;
typedef vector<char>                   VC;
typedef pair<int,int>                  PII;
typedef pair<LL,LL>                    PLL;
typedef pair<STR,int>                  PSI;
typedef pair<int,STR>                  PIS;
typedef vector<PII>                    VII;
typedef map<int,int>                   MII;
typedef map<LL,LL>                     MLL;
typedef map<STR,int>                   MSI;
typedef map<char,int>                  MCI;
typedef map<int,STR>                   MIS;
typedef set<STR>                       SS;
typedef set<int>                       SI;
typedef set<LL>                        SLL;

#define FF                             first
#define SS                             second
#define PB                             push_back
#define PF                             push_front
#define MP                             make_pair
#define all(a)                         (a).begin(), (a).end()
#define dec(n)                         cout<<fixed<<setprecision(n);
#define f(i, n)                     for(LL i=0; i<n; i++)
#define fr(i,n)                     for(LL i=n-1; i>=0; i--)

#define fast ios_base::sync_with_stdio(false),cin.tie(0),cout.tie(0);srand(time(NULL))

const LL MOD     = 1000000007;
const LL SIZE    = 100000;
const int INF    = 0x3f3f3f3f;
const LL LL_INF  = 0x3f3f3f3f3f3f3f3f;
const LD PI      = acos(-1);
const LL MAXN    = numeric_limits<LL>::max();

template<class T>  T maxT(T a, T b){return (a>b?a:b);}
template<class T>  T minT(T a, T b){return (a<b?a:b);}
template<class T>  void setmin(T &a, T b){a=(a>b ?a:b);}
template<class T>  void setmax(T &a, T b){a=(a<b ?a:b);}

void fileio(){
    freopen("input.txt", "r", stdin);
    freopen("output.txt", "w", stdout);
    freopen("debug.txt", "w", stderr);
}

void ofileio(){
  freopen("input.txt","r", stdin);
  freopen("output.txt", "w", stdout); 
}

void clock_out(){
  cerr<<"\nTime Elapsed : " << 1.0*clock() / CLOCKS_PER_SEC << " s\n";
}


void debug_out() { cerr << endl; }

template <typename Head, typename... Tail>
void debug_out(Head H, Tail... T) {
  cerr << " " << H;
  debug_out(T...);
}
 
#ifndef ONLINE_JUDGE
#define debug(...) cerr << "[" << #__VA_ARGS__ << "]:", debug_out(__VA_ARGS__)
#define fio() fileio()
#define ofio ofileio()
#define clock() clock_out()
#else
#define debug(...) 1
#define fio() 1
#define ofio() ofileio()
#define clock() 1
#endif

void solve(){
   int h, w;
   cin>>h>>w;
   char arr[h+1][w+1];
   for(int i=1; i<=h; i++){
   		for(int j=1; j<=w; j++){
   			cin>>arr[i][j];
   		}
   }
   LL dp[h+1][w+1];
   memset(dp, 0, sizeof(dp));
   //cerr<<dp[0][1];
   dp[1][1]=1;
   for(int i=1; i<=h; i++){
   		for(int j=1; j<=w; j++){
   			if(arr[i][j]=='#' ||(i==1 && j==1)) continue;
   			else{
   				dp[i][j]=(dp[i-1][j]%MOD + dp[i][j-1]%MOD)%MOD;
   			}
   		}
   }
   cout<<dp[h][w];
}

int main(){
  fast;
  //fio();

  LL t=1;
  //cin>>t;
  while(t--){
      solve();
  }
  clock();
  return 0;
}