### BUGGY CODE ###

def main():
    import sys
    input=sys.stdin.readline
    from collections import deque
    #class ctmp():
    #    def __init__(self,ij,dis):
    #        self.ij=ij
    #        self.dis=dis
    H,W=map(int,input().split())
    ls=["#"*(W+2)]#
    for i in range(H):
        ls.append("#"+input()+"#")
    ls.append("#"*(W+2))#
    q=deque([])
    qd=deque([])
    #tmp=ctmp((1,1),0)
    q.append((1,1))
    qd.append(0)
    #df={}
    lf=[[0 for _ in range(W+2)] for _ in range(H+2)]#
    lf[1][1]=0
    while q:
        tmpij=q.popleft()
        tmpd=qd.popleft()
        #df[tmpij]=1
        lf[tmpij[0]][tmpij[1]]=1
        if tmpij==(H,W):
            break
        lind=[(-1,0),(1,0),(0,-1),(0,1)]#
        for i in range(4):
            #ntmpij=(tmpij[0]+(i<2)*(2*i-1),tmpij[1]+(i>1)*(2*i-5))
            ntmpij=(tmpij[0]+lind[i][0],tmpij[1]+lind[i][1])
            #print(ntmpij)
            #if ntmpij not in df and ls[ntmpij[0]][ntmpij[1]]==".":
            if lf[ntmpij[0]][ntmpij[1]]==0 and ls[ntmpij[0]][ntmpij[1]]==".":
                #c_tmp=ctmp(ntmpij,tmp.dis+1)
                #q.append(c_tmp)
                q.append(ntmpij)
                qd.append(tmpd+1)
                #lf[ntmpij[0]][ntmpij[1]]=lf[tmpij[0]][tmpij[1]]+1
    if tmpij==(H,W):
        nw=0
        for i in range(1,H+1):
            #for j in range(1,W+1):
             #   if ls[i][j]==".":
              #      nw+=1
            nw+=ls[i].count(".")
        print(nw-tmpd-1)
        #print(nw-lf[H][W]-1)
    else:
        print(-1)

if __name__=='__main__':
    main()


### FIXED CODE ###

def main():
    import sys
    input=sys.stdin.readline
    from collections import deque
    #class ctmp():
    #    def __init__(self,ij,dis):
    #        self.ij=ij
    #        self.dis=dis
    H,W=map(int,input().split())
    ls=["#"*(W+2)]#
    for i in range(H):
        ls.append("#"+input()+"#")
    ls.append("#"*(W+2))#
    q=deque([])
    #qd=deque([])
    #tmp=ctmp((1,1),0)
    q.append((1,1))
    #qd.append(0)
    #df={}
    lf=[[float("inf") for _ in range(W+2)] for _ in range(H+2)]#
    #これでfとdの両方の役割をこなす
    lf[1][1]=0
    while q:
        tmpij=q.popleft()
        #tmpd=qd.popleft()
        #df[tmpij]=1
        if tmpij==(H,W):
            break
        lind=[(-1,0),(1,0),(0,-1),(0,1)]#
        for i in range(4):
            #ntmpij=(tmpij[0]+(i<2)*(2*i-1),tmpij[1]+(i>1)*(2*i-5))
            ntmpij=(tmpij[0]+lind[i][0],tmpij[1]+lind[i][1])
            #print(ntmpij)
            #if ntmpij not in df and ls[ntmpij[0]][ntmpij[1]]==".":
            if lf[ntmpij[0]][ntmpij[1]]==float("inf") and ls[ntmpij[0]][ntmpij[1]]==".":
                #c_tmp=ctmp(ntmpij,tmp.dis+1)
                #q.append(c_tmp)
                q.append(ntmpij)
                #qd.append(tmpd+1)
                lf[ntmpij[0]][ntmpij[1]]=lf[tmpij[0]][tmpij[1]]+1
                #dは訪れる前に書き込んでしまう
    if tmpij==(H,W):
        nw=0
        for i in range(1,H+1):
            #for j in range(1,W+1):
             #   if ls[i][j]==".":
              #      nw+=1
            nw+=ls[i].count(".")
        #print(nw-tmpd-1)
        print(nw-lf[H][W]-1)
    else:
        print(-1)

if __name__=='__main__':
    main()