import bisect
def solve():
    h, w, n = map(int, input().split())
    a = [list(map(int, input().split())) for _ in range(h)]
    
    for i in range(h):
        for j in range(w):
            a[i][j] -= 1
    
    dp = [0 for _ in range(n + 1)]
    
    dp[0] = 1
    
    nxt = [n for _ in range(n + 1)]
    
    for i in range(h - 1):
        for j in range(w):
            x = min(a[i][j], a[i + 1][j])
            y = max(a[i][j], a[i + 1][j])
            if x != y:
                nxt[x] = min(nxt[x], y)
    
    for i in range(h):
        for j in range(w - 1):
            x = min(a[i][j], a[i][j + 1])
            y = max(a[i][j], a[i][j + 1])
            if x != y:
                nxt[x] = min(nxt[x], y)
    
    for i in range(n):
        dp[i + 1] = max(dp[i + 1], dp[i])
        if nxt[i] != n:
            dp[nxt[i]] = max(dp[nxt[i]], dp[i] + 1)
            
    print(dp[n])
    


if __name__ == '__main__':
    solve()