CUBE-177: Escape

#include <bits/stdc++.h>

using namespace std;

int dp[1005][1005];
int n,m;

int main(){
    scanf("%d%d",&n,&m);
    for(int i=1;i<=n;i++){
        for(int j=1;j<=m;j++){
            scanf("%d",&dp[i][j]);
            if(dp[i][j])    dp[i][j] = -1;
        }
    }
    for(int i=1;i<=n;i++){
        for(int j=1;j<=m;j++){
            if(dp[i][j]==-1)
                continue;
            if(i==1 and j==1)
                dp[i][j] = 1;
            else{
                if(dp[i][j-1]!=-1)
                    dp[i][j] += dp[i][j-1];
                if(dp[i-1][j]!=-1)
                    dp[i][j] += dp[i-1][j];
                dp[i][j] %= 1000000007;
            }
        }
    }
    printf("%d",dp[n][m]);
}