#include <bits/stdc++.h>

#define FOR(i,a,b) for(int i= (a); i<((int)b); ++i)
#define RFOR(i,a) for(int i=(a); i >= 0; --i)
#define FOE(i,a) for(auto i : a)
#define ALL(c) (c).begin(), (c).end()
#define RALL(c) (c).rbegin(), (c).rend()
#define DUMP(x)  cerr << #x << " = " << (x) << endl;
#define SUM(x) std::accumulate(ALL(x), 0LL)
#define MIN(v) *std::min_element(v.begin(), v.end())
#define MAX(v) *std::max_element(v.begin(), v.end())
#define EXIST(v,x) (std::find(v.begin(), v.end(), x) != v.end())
#define BIT_ON(bit, i) (bit & (1LL << i))

typedef long long LL;
template<typename T> using V = std::vector<T>;
template<typename T> using VV = std::vector<std::vector<T>>;
template<typename T> using VVV = std::vector<std::vector<std::vector<T>>>;
template<typename T> using VVVV = std::vector<std::vector<std::vector<std::vector<T>>>>;

template<class T> inline T ceil(T a, T b) { return (a + b - 1) / b; }
template<class T> inline void print(T x) { std::cout << x << std::endl; }
template<class T> inline void print_vec(const std::vector<T> &v) { for (int i = 0; i < v.size(); ++i) {  if (i != 0) {std::cout << " ";} std::cout << v[i];} std::cout << "\n"; }
template<class T> inline bool inside(T y, T x, T H, T W) {return 0 <= y and y < H and 0 <= x and x < W; }
template<class T> inline double euclidean_distance(T y1, T x1, T y2, T x2) { return sqrt((x1 - x2) * (x1 - x2) + (y1 - y2) * (y1 - y2)); }
template<class T> inline double manhattan_distance(T y1, T x1, T y2, T x2) { return abs(x1 - x2) + abs(y1 - y2); }
template<class T> inline std::vector<T> unique(std::vector<T> v) {
    sort(v.begin(), v.end());
    v.erase(unique(v.begin(), v.end()), v.end());
    return v;
}

const int INF = 1 << 30;
const double EPS = 1e-9;
const std::string YES = "YES", Yes = "Yes", NO = "NO", No = "No";
const std::vector<int> dy4 = { 0, 1, 0, -1 }, dx4 = { 1, 0, -1, 0 };    // 4近傍（右, 下, 左, 上）
const std::vector<int> dy8 = { 0, -1, 0, 1, 1, -1, -1, 1 }, dx8 = { 1, 0, -1, 0, 1, 1, -1, -1 };

using namespace std;


LL solve(int H, int W, int start, int goal, map<int, V<pair<int, int>>> f) {
    VV<LL> dp(H, V<LL>(W, LONG_LONG_MAX));
    dp[f[start][0].first][f[start][0].second] = 0;

    FOR(i, start, goal) {
        FOE(p1, f[i]) {
            LL now_dist = dp[p1.first][p1.second];
            assert(now_dist != LONG_LONG_MAX);

            FOE(p2, f[i + 1]) {
                LL dist = abs(p1.first - p2.first) + abs(p1.second - p2.second);
                dp[p2.first][p2.second] = min(dp[p2.first][p2.second], now_dist + dist);
            }
        }
    }

    return dp[f[goal][0].first][f[goal][0].second];
}

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

    while (true) {
        int W, H;
        cin >> W >> H;
        if (H + W == 0) {
            break;
        }
        map<int, V<pair<int, int>>> f;
        pair<int, int> start, goal;
        int first = INF, last = 0;
        FOR(y, 0, H) {
            FOR(x, 0, W) {
                string s;
                cin >> s;
                if (s == "S") {
                    start = make_pair(y, x);
                }
                else if (s == "G") {
                    goal = make_pair(y, x);
                }
                else if (s == ".") {

                }
                else {
                    f[stoi(s)].emplace_back(make_pair(y, x));
                    first = min(first, stoi(s));
                    last = max(last, stoi(s));
                }
            }
        }
        if (first == INF) {
            first = 1;
            last = 0;
        }
        f[first - 1].emplace_back(start);
        f[last + 1].emplace_back(goal);


        print(solve(H, W, first - 1, last + 1, f));
    }

    return 0;
}


Measured memory_bytes: 3796