#include <bits/stdc++.h>
using namespace std;

#define CPP_STR(x) CPP_STR_I(x)
#define CPP_CAT(x, y) CPP_CAT_I(x, y)
#define CPP_STR_I(args...) #args
#define CPP_CAT_I(x, y) x##y

#define ASSERT(expr...) assert((expr))

using i8 = int8_t;
using u8 = uint8_t;
using i16 = int16_t;
using u16 = uint16_t;
using i32 = int32_t;
using u32 = uint32_t;
using i64 = int64_t;
using u64 = uint64_t;

using f32 = float;
using f64 = double;
// }}}

constexpr i64 INF = 1'010'000'000'000'000'017LL;

constexpr i64 MOD = 998244353LL;

constexpr f64 EPS = 1e-12;

constexpr f64 PI = 3.14159265358979323846;

#define M5 100007
#define M9 1000000000

#define F first
#define S second

// util {{{
#define FOR(i, start, end) for (i64 i = (start), CPP_CAT(i, xxxx_end) = (end); i < CPP_CAT(i, xxxx_end); ++i)
#define REP(i, n) FOR(i, 0, n)

#define all(x) (x).begin(), (x).end()
#define ll long long int
#define VI vector<ll>
#define VVI vector<VI>

#define ISD true
#define debug(x) \
    if (ISD)     \
    cout << #x << ": " << x << endl

template <typename T, typename U, typename Comp = less<>>
bool chmax(T &xmax, const U &x, Comp comp = {})
{
    if (comp(xmax, x))
    {
        xmax = x;
        return true;
    }
    return false;
}

template <typename T, typename U, typename Comp = less<>>
bool chmin(T &xmin, const U &x, Comp comp = {})
{
    if (comp(x, xmin))
    {
        xmin = x;
        return true;
    }
    return false;
}

int main()
{
    ll H, W, M;
    cin >> H >> W >> M;
    vector<string> S(H);
    REP(i, H)
    cin >> S[i];

    int sx, sy;
    int gx, gy;
    REP(i, H)
    REP(j, W)
    {
        if (S[i][j] == 'S')
        {
            sx = i;
            sy = j;
        }
        if (S[i][j] == 'G')
        {
            gx = i;
            gy = j;
        }
    }

    using P = tuple<int, int, int>;
    vector<VVI> d(H, VVI(W, VI(10, INF)));
    queue<P> que;
    que.push({sx, sy, 0}); // sから探索する
    d[sx][sy][0] = 0;
    int dx[4] = {1, 0, -1, 0};
    int dy[4] = {0, 1, 0, -1};
    while (que.size() != 0)
    {                          // 幅優先探索
        P state = que.front(); // 現在の状態
        que.pop();
        int x = get<0>(state);
        int y = get<1>(state);
        int t = get<2>(state);
        REP(k, 4)
        {
            int nx = x + dx[k];
            int ny = y + dy[k];
            if (nx < 0 || ny < 0 || nx >= H || ny >= W || S[nx][ny] == '#')
                continue;
            int nt = t;
            if ('1' <= S[nx][ny] && S[nx][ny] <= '9')
            {
                nt = S[nx][ny] - '0';
            }
            if ('a' <= S[nx][ny] && S[nx][ny] <= 'z' && S[nx][ny] - 'a' + 1 != t)
            {
                continue;
            }

            if (d[nx][ny][nt] != INF)
            {
                continue;
            }
            d[nx][ny][nt] = d[x][y][t] + 1;
            que.push({nx, ny, nt});
        }
    }

    ll ans = INF;
    REP(i, 10)
    {
        chmin(ans, d[gx][gy][i]);
    }
    if (ans == INF)
    {
        cout << -1 << endl;
    }
    else
    {
        cout << ans << endl;
    }
}