import java.io.BufferedReader
import java.io.InputStream
import java.io.InputStreamReader
import java.lang.AssertionError
import java.util.*
import kotlin.math.abs
import kotlin.math.max
import kotlin.math.min

val MOD = 1_000_000_007

class Solver(stream: InputStream, private val out: java.io.PrintWriter) {
  private val reader = BufferedReader(InputStreamReader(stream), 32768)

  fun solve() {
    val (H, W) = na(2)
    val grid = Array(H){ns()}
    val N = H + W - 1
    val dp = Array(N){Array(H){LongArray(H)}}
    if (N == 1) {
      out.println(1)
      return
    }

    val (m00, m01) = if (N % 2 == 1) {
      val m = N/2
      for (h in 0 until H) {
        val w = m - h
        if (w !in 0 until W) continue
        dp[m][h][h] = 1
      }
      Pair(N/2 - 1, N/2 + 1)
    }
    else {
      val m = N/2 - 1
      for (h in 0 until H) {
        val w = m - h
        if (w !in 0 until W) continue
        debug{"m:$m h:$h"}
        if (h + 1 in 0 until H && grid[h][w] == grid[h + 1][w]) dp[m][h][h + 1] = 1
        if (w + 1 in 0 until W && grid[h][w] == grid[h][w + 1]) dp[m][h][h] = 1
      }
      Pair(N/2 - 2, N/2 + 1)
    }
    debug{"$m00:$m01"}
    for (i in 0 until N) {
      debug{"dp[$i]"}
      debug { dp[i].map { it.joinToString(" ") }.joinToString("\n") }
    }

    for (i in 0 .. min(N - m01, m00)) {
      val m0 = m00 - i
      val m1 = m01 + i
      for (h0 in 0 until H) {
        val w0 = m0 - h0
        if (w0 !in 0 until W) continue

        for (h1 in 0 until H) {
          val w1 = m1 - h1
          if (w1 !in 0 until W) continue

          if (grid[h0][w0] != grid[h1][w1]) continue

          for (dh0 in 0 until 2) {
            for (dh1 in -1 .. 0) {
              if (h0 + dh0 !in 0 until N) continue
              if (h1 + dh1 !in 0 until N) continue

              dp[m0][h0][h1] = (dp[m0][h0][h1] + dp[m0 + 1][h0 + dh0][h1 + dh1]) % MOD
            }
          }
        }
      }
    }
    out.println(dp[0][0][H - 1])
  }













































  private val isDebug = try {
    // なんか本番でエラーでる
    System.getenv("MY_DEBUG") != null
  } catch (t: Throwable) {
    false
  }

  private var tokenizer: StringTokenizer? = null
  private fun next(): String {
    while (tokenizer == null || !tokenizer!!.hasMoreTokens()) {
      tokenizer = StringTokenizer(reader.readLine())
    }
    return tokenizer!!.nextToken()
  }

  private fun ni() = next().toInt()
  private fun nl() = next().toLong()
  private fun ns() = next()
  private fun na(n: Int, offset: Int = 0): IntArray {
    return IntArray(n) { ni() + offset }
  }
  private fun nal(n: Int, offset: Int = 0): LongArray {
    val res = LongArray(n)
    for (i in 0 until n) {
      res[i] = nl() + offset
    }
    return res
  }

  private fun na2(n: Int, offset: Int = 0): Array<IntArray> {
    val a  = Array(2){IntArray(n)}
    for (i in 0 until n) {
      for (e in a) {
        e[i] = ni() + offset
      }
    }
    return a
  }

  private inline fun debug(msg: () -> String) {
    if (isDebug) System.err.println(msg())
  }

  /**
   * コーナーケースでエラー出たりするので、debug(dp[1])のように添え字付きの場合はdebug{}をつかうこと
   */
  private inline fun debug(a: LongArray) {
    debug { a.joinToString(" ") }
  }

  private inline fun debug(a: IntArray) {
    debug { a.joinToString(" ") }
  }

  private inline fun debug(a: BooleanArray) {
    debug { toString(a) }
  }

  private inline fun toString(a: BooleanArray) = run{a.map { if (it) 1 else 0 }.joinToString("")}

  private inline fun debugDim(A: Array<LongArray>) {
    if (isDebug) {
      for (a in A) {
        debug(a)
      }
    }
  }
  private inline fun debugDim(A: Array<IntArray>) {
    if (isDebug) {
      for (a in A) {
        debug(a)
      }
    }
  }
  private inline fun debugDim(A: Array<BooleanArray>) {
    if (isDebug) {
      for (a in A) {
        debug(a)
      }
    }
  }

  /**
   * 勝手にimport消されるのを防ぎたい
   */
  private fun hoge() {
    min(1, 2)
    max(1, 2)
    abs(-10)
  }

  private inline fun assert(b: Boolean) = run{if (!b) throw AssertionError()}
  private inline fun assert(b: Boolean, f: () -> String) = run{if (!b) throw AssertionError(f())}

  companion object {
    // TestRunnerから呼びたいので単純なmainじゃだめ
    fun main() {
      val out = java.io.PrintWriter(System.out)
      Solver(System.`in`, out).solve()
      out.flush()
    }
  }
}

/**
 * judgeから呼ばれる
 */
fun main() = Solver.main()