#include <stdio.h>
#include <stdlib.h>
#define M 1000

char getDirection(const char dir, char mat[][M], const int i, const int j)
{
    char output = mat[i][j];

    if (mat[i][j] == '#')
    {
        output = dir;
    }

    mat[i][j] = 'X';
    return output;
}

int getIndex(const int index, const char dir, const int maxAtDirection)
{
    if (dir == 'D' || dir == 'R')
    {
        if (index + 1 >= maxAtDirection)
        {
            return 0;
        }

        return (index + 1);
    }

    if (dir == 'U' || dir == 'L')
    {
        if (index - 1 < 0)
        {
            return (maxAtDirection - 1);
        }

        return (index - 1);
    }

    return index;
}

int getChanged(const char dir)
{
    if (dir == 'U' || dir == 'D')
    {
        return 1;
    }

    if (dir == 'R' || dir == 'L')
    {
        return 2;
    }

    return 0;
}

int breakConditionCheck(char mat[][M], const int i, const int j, int length)
{
    if (i == 0 && j == 0)
    {
        return ++length;
    }
    if (mat[i][j] == 'X')
    {
        return -1;
    }

    return -2;
}

int letPacmanPathRec(
    char mat[][M],
    const int n, const int m,
    int length,
    int i, int j, char dir)
{
    dir = getDirection(dir, mat, i, j);
    if (getChanged(dir) == 1)
    {
        i = getIndex(i, dir, n);
    }
    else if (getChanged(dir) == 2)
    {
        j = getIndex(j, dir, m);
    }

    const int val = breakConditionCheck(mat, i, j, length);
    if (val != -2)
    {
        return val;
    }

    return letPacmanPathRec(mat, n, m, ++length, i, j, dir);
}

int lenPacmanPath(char mat[][M], const int n, const int m)
{
    return letPacmanPathRec(mat, n, m, 0, 0, 0, '#');
}


// Do not change these functions
void fillMatrix(char mat[][M], const int n, const int m)
{
    for (int i = 0; i < n; i++)
    {
        for (int j = 0; j < m; j++)
        {
            scanf(" %c", &mat[i][j]);
        }
    }
}

// Do not change the main function
int main()
{
    int n = 0, m = 0;
    int student_output = -2;

    scanf(" %d %d", &n, &m);

    char (*mat)[M] = malloc(n * M * sizeof(char));
    if (mat)
    {
        fillMatrix(mat, n, m);
        student_output = lenPacmanPath(mat, n, m);
    }
    printf("%d", student_output);

    free(mat);
    return 0;
}