#include <cstdio>
#include <cstdlib>
#include <cstring>
#include <cmath>
#include <climits>
#include <cfloat>
#include <ctime>
#include <cassert>
#include <map>
#include <utility>
#include <set>
#include <iostream>
#include <memory>
#include <string>
#include <vector>
#include <algorithm>
#include <functional>
#include <sstream>
#include <complex>
#include <stack>
#include <queue>
#include <numeric>
#include <list>
#include <iomanip>
 
using namespace std;
 
#if __GNUC__
#include <tr1/unordered_map>
#include <tr1/unordered_set>
using namespace tr1;
#else
#include <unordered_map>
#include <unordered_set>
#endif
 
#ifdef __GNUC__
template <class T> int popcount(T n);
template <> int popcount(unsigned int n) { return __builtin_popcount(n); }
template <> int popcount(int n) { return __builtin_popcount(n); }
template <> int popcount(unsigned long long n) { return __builtin_popcountll(n); }
template <> int popcount(long long n) { return __builtin_popcountll(n); }
#else
#define __typeof__ decltype
template <class T> int popcount(T n) { return n ? 1 + popcount(n & (n - 1)) : 0; }
#endif
 
#define rep(i, n) for (int i = 0; i < (int)n; ++i)
#define foreach(it, c) for (__typeof__((c).begin()) it=(c).begin(); it != (c).end(); ++it)
#define rforeach(it, c) for (__typeof__((c).rbegin()) it=(c).rbegin(); it != (c).rend(); ++it)
#define all(c) (c).begin(), (c).end()
#define rall(c) (c).rbegin(), (c).rend()
#define CL(arr, val) memset(arr, val, sizeof(arr))
#define COPY(dest, src) memcpy(dest, src, sizeof(dest))
 
template <class T> void max_swap(T& a, const T& b) { a = max(a, b); }
template <class T> void min_swap(T& a, const T& b) { a = min(a, b); }
 
typedef long long ll;
typedef pair<int, int> pint;
 
template <class T, class U> ostream& operator<<(ostream& os, pair<T, U>& p) { os << "( " << p.first << ", " << p.second << " )"; return os;  }
 
template <class T> string to_s(const T& a) { ostringstream os; os << a; return os.str(); }
 
 
const int mod = 1000000007;
const double PI = acos(-1.0);
const int dx[] = { 0, 1, 0, -1 };
const int dy[] = { 1, 0, -1, 0 };
bool valid_pos(int x, int y, int w, int h) { return 0 <= x && x < w && 0 <= y && y < h; }
 
template <class T> void print(T a, int n, int br = 1, const string& deli = ", ") { cout << "{ "; for (int i = 0; i < n; ++i) { cout << a[i]; if (i + 1 != n) cout << deli; } cout << " }"; while (br--) cout << endl; }
template <class T> void print(const vector<T>& v, int br = 1, const string& deli = ", ") { print(v, v.size(), br, deli); }
template <class T> void print2d(T a, int w, int h, int width = -1, int br = 1) { for (int i = 0; i < h; ++i) { for (int j = 0; j < w; ++j) {	if (width != -1) cout.width(width); cout << a[i][j] << ' ';	} cout << endl; } while (br--) cout << endl; }
 
template <class T> void input(T& a, int n) { for (int i = 0; i < n; ++i) cin >> a[i]; }
template <class T, class U> void input(T& a, U& b, int n) { for (int i = 0; i < n; ++i) cin >> a[i] >> b[i]; }
 


int w, h, sx, sy, gx, gy;
char c[16][16];
int f[16][16];
vector<int> limit;

void mark_ice(int _x, int _y)
{
	int size = 0;
	int id = limit.size();

	queue<pint> q;
	q.push(pint(_x, _y));
	while (!q.empty())
	{
		int x = q.front().first, y = q.front().second;
		q.pop();

		f[y][x] = id;
		++size;

		for (int i = 0; i < 4; ++i)
		{
			int nx = x + dx[i], ny = y + dy[i];
			if (valid_pos(nx, ny, w, h) && c[ny][nx] == 'X' && f[ny][nx] == -1)
				q.push(pint(nx, ny));
		}
	}

	limit.push_back((size + 2) / 2);
}

int res;
int walk[256];
bool visit[16][16];
int dir[16][16][4];
int gdis[16][16];

void dfs(int x, int y, int dis)
{
	if (gdis[y][x] + dis >= res)
		return;
	else if (x == gx && y == gy)
	{
		res = dis;
		return;
	}

	for (int i = 0; i < 4; ++i)
	{
		int d = dir[y][x][i];
		int nx = x + dx[d], ny = y + dy[d];
		if (valid_pos(nx, ny, w, h) && !visit[ny][nx] && f[ny][nx] != -1)
		{
			int id = f[ny][nx];
			++walk[id];
			if (walk[id] < limit[id])
			{
				visit[ny][nx] = true;
				dfs(nx, ny, dis + 1);
				visit[ny][nx] = false;
			}
			--walk[id];
		}
	}
}
int dis_ignore_ice(int sx, int sy)
{
	int d[16][16];
	CL(d, -1);
	queue<pint> q;
	d[sy][sx] = 0;
	q.push(pint(sx, sy));
	while (!q.empty())
	{
		int x = q.front().first, y = q.front().second;
		q.pop();

		if (x == gx && y == gy)
			return d[y][x];

		for (int i = 0; i < 4; ++i)
		{
			int nx = x + dx[i], ny = y + dy[i];
			if (valid_pos(nx, ny, w, h) && c[ny][nx] != '#' && d[ny][nx] == -1)
			{
				d[ny][nx] = d[y][x] + 1;
				q.push(pint(nx, ny));
			}
		}
	}

	return 114514;
}
int main()
{
	ios::sync_with_stdio(false);

	while (cin >> w >> h, w)
	{
		limit.clear();
		CL(visit, 0);
		CL(f, -1);

		for (int i = 0; i < h; ++i)
			cin >> c[i];

		limit.push_back(114514);
		for (int y = 0; y < h; ++y)
		{
			for (int x = 0; x < w; ++x)
			{
				if (strchr("SG.", c[y][x]))
					f[y][x] = 0;

				if (c[y][x] == 'S')
					sx = x, sy = y;
				else if (c[y][x] == 'G')
					gx = x, gy = y;
				else if (c[y][x] == 'X' && f[y][x] == -1)
					mark_ice(x, y);
				else if (c[y][x] == '#')
					f[y][x] = -1;
			}
		}

		for (int y = 0; y < h; ++y)
			for (int x = 0; x < w; ++x)
				gdis[y][x] = dis_ignore_ice(x, y);
		for (int y = 0; y < h; ++y)
		{
			for (int x = 0; x < w; ++x)
			{
				pint dd[4];
				for (int i = 0; i < 4; ++i)
				{
					int nx = x + dx[i], ny = y + dy[i];
					dd[i] = pint(valid_pos(nx, ny, w, h) ? gdis[ny][nx] : 114514, i);
				}
				sort(dd, dd + 4);
				for (int i = 0; i < 4; ++i)
					dir[y][x][i] = dd[i].second;
			}
		}

		res = 114514;
		visit[sy][sx] = true;
		dfs(sx, sy, 0);
		cout << res << endl;
	}
}

Measured memory_bytes: 0