#include<bits/stdc++.h>
using namespace std;
using ll = long long;
using VI = vector<ll>;
using VV = vector<VI>;
using VS = vector<string>;
using PII = pair<ll, ll>;

// tourist set
template <typename A, typename B>
string to_string(pair<A, B> p);

template <typename A, typename B, typename C>
string to_string(tuple<A, B, C> p);

template <typename A, typename B, typename C, typename D>
string to_string(tuple<A, B, C, D> p);

string to_string(const string& s) {
  return '"' + s + '"';
}

string to_string(const char* s) {
  return to_string((string) s);
}

string to_string(bool b) {
  return (b ? "true" : "false");
}

string to_string(vector<bool> v) {
  bool first = true;
  string res = "{";
  for (int i = 0; i < static_cast<int>(v.size()); i++) {
    if (!first) {
      res += ", ";
    }
    first = false;
    res += to_string(v[i]);
  }
  res += "}";
  return res;
}

template <size_t N>
string to_string(bitset<N> v) {
  string res = "";
  for (size_t i = 0; i < N; i++) {
    res += static_cast<char>('0' + v[i]);
  }
  return res;
}

template <typename A>
string to_string(A v) {
  bool first = true;
  string res = "{";
  for (const auto &x : v) {
    if (!first) {
      res += ", ";
    }
    first = false;
    res += to_string(x);
  }
  res += "}";
  return res;
}

template <typename A, typename B>
string to_string(pair<A, B> p) {
  return "(" + to_string(p.first) + ", " + to_string(p.second) + ")";
}

template <typename A, typename B, typename C>
string to_string(tuple<A, B, C> p) {
  return "(" + to_string(get<0>(p)) + ", " + to_string(get<1>(p)) + ", " + to_string(get<2>(p)) + ")";
}

template <typename A, typename B, typename C, typename D>
string to_string(tuple<A, B, C, D> p) {
  return "(" + to_string(get<0>(p)) + ", " + to_string(get<1>(p)) + ", " + to_string(get<2>(p)) + ", " + to_string(get<3>(p)) + ")";
}

void debug_out() { cerr << '\n'; }

template <typename Head, typename... Tail>
void debug_out(Head H, Tail... T) {
  cerr << " " << to_string(H);
  debug_out(T...);
}

#ifdef LOCAL
#define debug(...) cerr << "[" << #__VA_ARGS__ << "]:", debug_out(__VA_ARGS__)
#else
#define debug(...) 42
#endif
// tourist set end

template<class T>bool chmax(T &a, const T &b) { if (a<b) { a=b; return 1; } return 0; }
template<class T>bool chmin(T &a, const T &b) { if (b<a) { a=b; return 1; } return 0; }

#define FOR(i,a,b) for(ll i=(a);i<(b);++i)
#define rep(i,b) FOR(i, 0, b)
#define ALL(v) (v).begin(), (v).end()
#define p(s) cout<<(s)<<'\n'
#define p2(s, t) cout << (s) << " " << (t) << '\n'
#define br() p("")
#define pn(s) cout << (#s) << " " << (s) << '\n'
#define p_yes() p("YES")
#define p_no() p("NO")
#define SZ(x) ((int)(x).size())
#define SORT(A) sort(ALL(A))
#define RSORT(A) sort(ALL(A), greater<ll>())
#define MP make_pair

void no(){p_no(); exit(0);}
void yes(){p_yes(); exit(0);}

const ll mod = 1e9 + 7;
const ll inf = 1e18;
const double PI = acos(-1);

ll A[100][100];
ll d[100][100];

void reset(){
  rep(i, 100){
    rep(j, 100){
      d[i][j]=-1;
    }
  }
}

ll W, H;

bool in_range(ll i, ll j){
  if(0<=i && i<H && 0<=j && j<W){
    return true;
  }else{
    return false;
  }
}

int dx[4] = {-1, 0, 1,  0};
int dy[4] = { 0, 1, 0, -1};

bool can_go(ll y, ll x, ll dir){
  // debug(y, x, dir);
  if(dir==0 || dir==2){
    // 左右移動
    ll row = 2*y;
    if(dir==0){
      // 左
      if(x==0){
        return false;
      }else{
        if(A[row][x-1]==1){
          return false;
        }else{
          return true;
        }
      }
    }
    else{
      // 右
      if(x==W-1){
        return false;
      }else{
        if(A[row][x]==1){
          return false;
        }else{
          return true;
        }
      }
    }
  }
  else{
    // 上下移動
    ll row;
    if(dir==3){
      row = 2*(y-1) + 1;
      // 上
      if(y==0){
        return false;
      }else{
        if(A[row][x]==1){
          return false;
        }else{
          return true;
        }
      }
    }
    else{
      row = 2*y + 1;
      // 下
      if(y==H-1){
        return false;
      }else{
        if(A[row][x]==1){
          return false;
        }else{
          return true;
        }
      }
    }
  }
}

int main(){
    cin.tie(0);
    ios::sync_with_stdio(false);

    // input

    while(cin>>W>>H){
      if(W==0) return 0;
      reset();
      rep(i, 2*H-1){
        if(i%2==0){
          // たてかべ
          rep(j, W-1){
            cin >> A[i][j];
          }
        }
        else{
          rep(j, W){
            cin >> A[i][j];
          }
        }
      }

      d[0][0]=0;
      // bfs
      queue<PII> que;
      que.push(MP(0, 0));
      while(!que.empty()){
        auto pa = que.front(); que.pop();
        ll i = pa.first;
        ll j = pa.second;
        ll dist = d[i][j];

        rep(dir, 4){
          ll ty = i + dy[dir];
          ll tx = j + dx[dir];
          if(in_range(ty, tx) && can_go(i, j, dir) && d[ty][tx]==-1){
            que.push(MP(ty, tx));
            d[ty][tx] = dist+1;
          }
        }
      }

      ll ans = d[H-1][W-1] + 1;
      p(ans);
    }
    
    return 0;
}


Measured memory_bytes: 3268