H,W = map(int,input().split())
board = []
for _ in range(H):
    tmp = list(input())
    board.append(tmp)
def convert(k,h1,h2):
    return (H**2) * k + H * h1 + h2
def ch1(k,h,mid):
    return (h,mid-k-h)
def ch2(k,h,mid):
    return (h,mid+k-h)
mod = 10 ** 9 + 7
def isin(h,w):
    if 0 <= h < H and 0 <= w < W:
        return True
    else:
        return False
def check(k,h1,h2,mid1,mid2):
    h1,w1 = ch1(k,h1,mid1)
    h2,w2 = ch2(k,h2,mid2)
    if isin(h1,w1) and isin(h2,w2) and board[h1][w1] == board[h2][w2]:
        return True
    else:
        return False
def solve():
    if (H + W ) % 2 == 0:
        mid = (H-1+W-1) //2
        dp = [0 for _ in range((H**2) * (mid+1))]
        for h1 in range(H):
            dp[convert(0,h1,h1)] = 1
        for k in range(mid):
            for h1 in range(H):
                for h2 in range(H):
                    for dh1,dh2 in [(-1,0),(-1,1),(0,0),(0,1)]:
                        nh1 = h1 + dh1
                        nh2 = h2 + dh2
                        if check(k+1,nh1,nh2,mid,mid):
                            dp[convert(k+1,nh1,nh2)] += dp[convert(k,h1,h2)]
                            dp[convert(k+1,nh1,nh2)] %= mod
        return dp[convert(mid,0,H-1)]
    else:
        mid1 = (H-1+W-1 -1) //2
        mid2 = (H-1+W-1 +1) //2
        dp = [0 for _ in range((H**2) * (mid1+1))]
        for h1 in range(H):
            for h2 in range(max(h1-1,0),h1+1):
                dp[convert(0,h1,h2)] = 1
        for k in range(mid1):
            for h1 in range(H):
                for h2 in range(H):
                    for dh1,dh2 in [(-1,0),(-1,1),(0,0),(0,1)]:
                        nh1 = h1 + dh1
                        nh2 = h2 + dh2
                        if check(k+1,nh1,nh2,mid1,mid2):
                            dp[convert(k+1,nh1,nh2)] += dp[convert(k,h1,h2)]
                            dp[convert(k+1,nh1,nh2)] %= mod
        return dp[(convert(mid1,0,H-1))]
print(solve())