#include <iostream>
#include <iomanip>
#include <sstream>
#include <cstdio>
#include <cstdlib>
#include <cmath>
#include <cstring>
#include <climits>
#include <cfloat>
#include <string>
#include <vector>
#include <stack>
#include <queue>
#include <set>
#include <map>
#include <algorithm>
#include <functional>
#include <utility>
#include <numeric>

using namespace std;

typedef unsigned int UI;
typedef long long LL;
typedef unsigned long long ULL;
typedef vector<int> VI;
typedef vector<VI> VVI;
typedef vector<string> VS;
typedef pair<int,int> PII;
typedef istringstream ISS;
typedef ostringstream OSS;

#define REP( i, m, n ) for ( int i = (int)( m ); i < (int)( n ); ++i )
#define FOR( v, c ) for ( auto &v : c )

#define ITER( c ) __typeof( (c).begin() )
#define EACH( it, c ) for ( ITER(c) it = c.begin(); it != c.end(); ++it )
#define ALL( c ) (c).begin(), (c).end()

#define PB( n ) push_back( n )
#define MP( a, b ) make_pair( ( a ), ( b ) )
#define EXIST( c, e ) ( (c).find( e ) != (c).end() )

#define fst first
#define snd second

#define DUMP( x ) cerr << #x << " = " << ( x ) << endl
#define DEBUG( x ) cerr << __FILE__ << ":" << __LINE__ << ": " << #x << " = " << ( x ) << endl

int distance( const PII &a, const PII &b )
{
	return abs( a.fst - b.fst ) + abs( a.snd - b.snd );
}

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

	while ( true )
	{
		int w, h;
		cin >> w >> h;
		
		if ( !( w | h ) )
		{
			break;
		}

		vector<VS> board( h, VS( w ) );
		FOR( line, board )
		{
			FOR( word, line )
			{
				cin >> word;
			}
		}

		int n = 0, maxsize = 1;
		PII s, g;
		map< int, vector< PII > > index;
		REP( i, 0, h )
		{
			REP( j, 0, w )
			{
				if ( board[i][j] == "." )
				{
					continue;
				}
				else if ( board[i][j] == "S" )
				{
					s = MP( i, j );
				}
				else if ( board[i][j] == "G" )
				{
					g = MP( i, j );
				}
				else
				{
					ISS iss( board[i][j] );
					int num;
					iss >> num;

					index[ num ].PB( MP( i, j ) );
					n = max( n, num );
					maxsize = max( maxsize, (int)index[ num ].size() );
				}
			}
		}
		index[0].PB( s );
		index[ n + 1 ].PB( g );

		VVI dp( n + 2, VI( maxsize, INT_MAX ) );
		dp[0][0] = 0;

		REP( i, 0, n + 1 )
		{
			REP( f, 0, index[i].size() )
			{
				REP( t, 0, index[ i + 1 ].size() )
				{
					dp[ i + 1 ][t] = min( dp[ i + 1 ][t], dp[i][f] + distance( index[i][f], index[ i + 1 ][t] ) );
				}
			}
		}

		cout << dp[ n + 1 ][0] << endl;
	}

	return 0;
}