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

#define inrep int t; cin >> t; for(int tc=1; tc<=t; tc++)

#define fi first
#define sc second
#define mp make_pair

int main()
{
	int n, m; cin >> n >> m; string s[n+8];
	pair<int, int> safe, rusa;
	for(int i=0; i<n; i++) {
		cin >> s[i];
		for(int j=0; j<n; j++) {
			if (s[i][j] == 'S')
				safe.fi = i, safe.sc = j;
			else if (s[i][j] == 'R')
				rusa.fi = i, rusa.sc = j;
		}
	}
	queue<pair<pair<int, pair<int, int> >, int > > q;
	q.push(mp(mp(m, mp(rusa.fi, rusa.sc)), 0));
	bool vis[1007][1007] = {0};
	int f = 0;
	while(q.size())
	{
		int x = q.front().fi.sc.fi, y = q.front().fi.sc.sc; int bats = q.front().fi.fi, hit = q.front().sc; q.pop();

		if (x < 0 || x >= n || y < 0 || y >= n) continue;

		if (x == safe.fi && y == safe.sc) {
			cout << hit << "\n";
			f = 1;
			break;
		}

		if (s[x][y-1] == '#' && bats > 0)
			q.push(mp(mp(bats-1, mp(x, y-1)), hit+1));
		else if (vis[x][y-1] == 0 && s[x][y-1] != '#')
			vis[x][y-1] = 1,
			q.push(mp(mp(bats, mp(x, y-1)), hit+1));

		if (s[x+1][y] == '#' && bats > 0)
			q.push(mp(mp(bats-1, mp(x+1, y)), hit+1));
		else if (vis[x+1][y] == 0 && s[x+1][y] != '#')
			vis[x+1][y] = 1,
			q.push(mp(mp(bats, mp(x+1, y)), hit+1));

		if (s[x][y+1] == '#' && bats > 0)
			q.push(mp(mp(bats-1, mp(x, y+1)), hit+1));
		else if (vis[x][y+1] == 0 && s[x][y+1] != '#')
			vis[x][y+1] = 1,
			q.push(mp(mp(bats, mp(x, y+1)), hit+1));

		if (s[x-1][y] == '#' && bats > 0)
			q.push(mp(mp(bats-1, mp(x-1, y)), hit+1));
		else if (vis[x-1][y] == 0 && s[x-1][y] != '#')
			vis[x-1][y] = 1,
			q.push(mp(mp(bats, mp(x-1, y)), hit+1));
	}
	if (f == 0) {
		cout << "IMPOSSIBLE" << "\n";
	}
}