using System;
using static System.Console;
using System.Linq;
using System.Collections.Generic;

class Program
{
    static int NN => int.Parse(ReadLine());
    static long[] NList => ReadLine().Split().Select(long.Parse).ToArray();
    static long[][] NArr(long n) => Enumerable.Repeat(0, (int)n).Select(_ => NList).ToArray();
    static string[] SList(long n) => Enumerable.Repeat(0, (int)n).Select(_ => ReadLine()).ToArray();
    public static void Main()
    {
        Solve();
    }
    static void Solve()
    {
        var c = NList;
        var (h, w, m) = (c[0], c[1], c[2]);
        var s = SList(h);

        var (sx, sy, gx, gy) = (0, 0, 0, 0);
        for (var i = 0; i < h; ++i) for (var j = 0; j < w; ++j)
            {
                if (s[i][j] == 'S')
                {
                    sx = i;
                    sy = j;
                }
                else if (s[i][j] == 'G')
                {
                    gx = i;
                    gy = j;
                }
            }
        var dp = new int[h, w, m + 1];
        var INF = int.MaxValue / 2;
        for (var i = 0; i < h; ++i) for (var j = 0; j < w; ++j) for (var k = 0; k <= m; ++k) dp[i, j, k] = INF;
        var mx = new int[] { 0, 0, -1, 1 };
        var my = new int[] { -1, 1, 0, 0 };
        var q = new Queue<(int x, int y, int k)>();
        q.Enqueue((sx, sy, 0));
        dp[sx, sy, 0] = 0;
        while (q.Count > 0)
        {
            var cur = q.Dequeue();
            if (cur.x == gx && cur.y == gy)
            {
                WriteLine(dp[cur.x, cur.y, cur.k]);
                return;
            }
            for (var i = 0; i < 4; ++i)
            {
                var nx = cur.x + mx[i];
                var ny = cur.y + my[i];
                if (nx < 0 || nx >= h || ny < 0 || ny >= w) continue;
                var nk = cur.k;
                if (s[nx][ny] >= '1' && s[nx][ny] <= '9')
                {
                    nk = s[nx][ny] - '0';
                }
                if (s[nx][ny] == '#' || (s[nx][ny] >= 'a' && s[nx][ny] <= 'i' && nk != s[nx][ny] - 'a' + 1)) continue;
                if (dp[nx, ny, nk] <= dp[cur.x, cur.y, cur.k] + 1) continue;
                dp[nx, ny, nk] = dp[cur.x, cur.y, cur.k] + 1;
                q.Enqueue((nx, ny, nk));
            }
        }
        WriteLine("-1");
    }
}