import core.bitop, std.algorithm, std.ascii, std.bigint, std.conv, std.math,
    std.functional, std.numeric, std.range, std.stdio, std.string, std.random,
    std.typecons, std.container, std.format, std.datetime;

// dfmt off
T lread(T = long)(){return readln.chomp.to!T();}
T[] lreads(T = long)(long n){return generate(()=>readln.chomp.to!T()).take(n).array();}
T[] aryread(T = long)(){return readln.split.to!(T[])();}
void scan(TList...)(ref TList Args){auto line = readln.split();
foreach (i, T; TList){T val = line[i].to!(T);Args[i] = val;}}
alias sread = () => readln.chomp();enum MOD = 10 ^^ 9 + 7;
alias PQueue(T, alias less = "a<b") = BinaryHeap!(Array!T, less);
// dfmt on

void main()
{
    long H, W;
    scan(H, W);
    auto S = new string[](H);
    foreach (i; 0 .. H)
        S[i] = sread();

    auto visited = new bool[][][](H, W, 2);

    PQueue!(Tuple!(long, long, long, long), "b<a") PQ;
    PQ.insert(Tuple!(long, long, long, long)(0, 0, 0, 0));
    long ans = long.max;
    while (!PQ.empty)
    {
        auto t = PQ.front();
        PQ.popFront();
        long d = t[0];
        long y = t[1];
        long x = t[2];
        long f = t[3];
        if (H <= y)
            continue;
        if (W <= x)
            continue;
        if (visited[y][x][f])
            continue;
        visited[y][x][f] = true;
        bool b = S[y][x] == '#';
        // writeln(b, t);
        if (y == H - 1 && x == W - 1)
        {
            ans = ans.min(d + (f != b && b));
        }
        PQ.insert(Tuple!(long, long, long, long)(d + (f == 0 && b), y + 1, x, (f == 0 && b)));
        PQ.insert(Tuple!(long, long, long, long)(d + (f == 0 && b), y, x + 1, (f == 0 && b)));
        // PQ.insert(Tuple!(long, long, long, long)(d + (f == 0 || !b), y + 1, x, 1));
        // PQ.insert(Tuple!(long, long, long, long)(d + (f == 0 || !b), y, x + 1, 1));
    }
    writeln(ans);
}
