#include <bits/stdc++.h>                                                                                                                                                                                                                                                                                           //Created by CUBERLONG
using namespace std;                                                                                                                                                                                                                                                                                               //Created by CUBERLONG
#define int long long
void _time() {
    #ifndef ONLINE_JUDGE
        cout << "_nTime: " << (int)clock() << "ms.n";                                                                                                                                                                                                                                                                                           //Created by CUBERLONG
    #endif
}
void fast() {
    ios_base::sync_with_stdio(0); cin.tie(0); cout.tie(0);
    #ifndef ONLINE_JUDGE
        freopen("ab.inp", "r", stdin);
        freopen("ab.out", "w", stdout);
    #endif
}
#define II pair<int,int>
#define x first
#define y second
const int N = 1505;
int r, c;
int f[N][N];
char a[N][N];
bool visited[N][N];
II dxy[] = {{-1, 0}, {0, -1}, {1, 0}, {0, 1}};
vector<II> L;
queue<II> qu1, qu2;

bool inside(II x) {
    return 0 <= x.x && x.x < r && 0 <= x.y && x.y < c;
}

void visit(II u, int len, bool next) {
    len += next;
    for (II d: dxy) {
        II v = {u.x + d.x, u.y + d.y};
        if (inside(v) && !visited[v.x][v.y] && f[v.x][v.y] <= len) {
            visited[v.x][v.y] = 1;
            qu1.push(v);
        }
    }
}
int bfs() {
    qu1.push(L[0]);
    visited[L[0].x][L[0].y] = 1;
    for (int len = 0; 1; ++len) {
        while (!qu1.empty()) {
            II u = qu1.front(); qu1.pop();
            qu2.push(u);
            visit(u, len, 0);
        }
        while (!qu2.empty()) {
            II u = qu2.front(); qu2.pop();
            if (u == L[1]) return len;
            visit(u, len, 1);
        }
    }
    return -1;
}
signed main() {
    fast();

    cin >> r >> c;
    memset(f, -1, sizeof f);
    queue<II> qu;
    for (int i = 0; i < r; ++i)
        for (int j = 0; j < c; ++j) {
            cin >> a[i][j];
            if (a[i][j] == 'L')
                L.push_back({i, j});
            if (a[i][j] != 'X') {
                f[i][j] = 0;
                qu.push({i, j});
            }
        }
    while (!qu.empty()) {
        II u = qu.front(); qu.pop();
        for (II d: dxy) {
            II v = {u.x + d.x, u.y + d.y};
            if (inside(v) && f[v.x][v.y] < 0) {
                f[v.x][v.y] = f[u.x][u.y] + 1;
                qu.push(v);
            }
        }
    }
    cout << bfs();

    return _time(), 0;
}                                                                                                                                                                                                                                                                                                               //Created by CUBERLONG
/*
*/