#include <bits/stdc++.h>

using namespace std;

typedef pair<int, int> pii;
typedef long long ll;
const int N = 2000086, MOD = 998244353, INF = 0x3f3f3f3f;
ll res;
int n, m, cnt, w[N];

char s[508][508];
int d[508][508][10], k;
int dx[4] = {1, 0, -1, 0}, dy[4] = {0, 1, 0, -1};

int main() {
	cin >> n >> m >> k;
	for (int i = 1; i < n + 1; i++) scanf("%s", s[i] + 1);
	memset(d, 0x3f, sizeof d);
	queue<array<int, 3> > q;
	for (int i = 1; i < n + 1; i++)
		for (int j = 1; j < m + 1; j++)
			if (s[i][j] == 'S')
				d[i][j][0] = 0, q.push({i, j, 0});
	while (q.size()) {
		auto u = q.front(); q.pop();
		int x = u[0], y = u[1], p = u[2];
		for (int i = 0; i < 4; i++) {
			int nx = x + dx[i], ny = y + dy[i];
			if (!nx || !ny || nx > n || ny > m || s[nx][ny] == '#') continue;
			if (s[nx][ny] == 'G') {
				printf("%d\n", d[x][y][p] + 1);
				return 0;
			}
			if (s[nx][ny] >= '1' && s[nx][ny] <= '9') {
				if (d[nx][ny][s[nx][ny] - '0'] == INF) {
					d[nx][ny][s[nx][ny] - '0'] = d[x][y][p] + 1;
					q.push({nx, ny, s[nx][ny] - '0'});
				}
			} else if (s[nx][ny] >= 'a' && s[nx][ny] <= 'i') {
				if (p == s[nx][ny] - 'a' + 1 && d[nx][ny][s[nx][ny] - 'a' + 1] == INF) {
					d[nx][ny][s[nx][ny] - 'a' + 1] = d[x][y][p] + 1;
					q.push({nx, ny, s[nx][ny] - 'a' + 1});
				}
			} else {
				if (d[nx][ny][p] == INF) {
					d[nx][ny][p] = d[x][y][p] + 1;
					q.push({nx, ny, p});
				}
			}
		}
	}
	puts("-1");
	return 0;
}