mod=10**9+7

h,w=map(int,input().split())
s=[]
for i in range(h):
  s.append(list(input()))

def conv(i,j,k):
  return h*w*i+h*j+k

dp=[0]*(h*w*h)
if (h+w)%2==0:
  for i1 in range(h):
    j1=(h+w-2)//2-i1
    if 0<=j1<w:
      dp[conv(i1,j1,i1)]=1
else:
  for i1 in range(h):
    j1=(h+w-3)//2-i1
    if 0<=j1<w:
      for i2,j2 in [(i1+1,j1),(i1,j1+1)]:
        if 0<=i2<h and 0<=j2<w and s[i1][j1]==s[i2][j2]:
          dp[conv(i1,j1,i2)]=1

for m in range((h+w-2)//2,0,-1):
  for i1 in range(h):
    j1=m-i1
    if 0<=j1<w:
      for i2 in range(h):
        j2=h+w-2-m-i2
        if 0<=j2<w:
          for ni1,nj1,ni2,nj2 in ((i1-1,j1,i2+1,j2),(i1,j1-1,i2+1,j2),(i1-1,j1,i2,j2+1),(i1,j1-1,i2,j2+1)):
            if 0<=ni1<h and 0<=nj1<w and 0<=ni2<h and 0<=nj2<w and s[ni1][nj1]==s[ni2][nj2]:
              dp[conv(ni1,nj1,ni2)]+=dp[conv(i1,j1,i2)]
              dp[conv(ni1,nj1,ni2)]%=mod
  
print(dp[conv(0,0,h-1)])