void solve()
{
cin = new Scanner();
N = cin.nextInt();
a = new int[N];
int sum = 0;
int ave = 0;
int chokudai = 0;
bool[] isReachable = new bool[N - 1];
for (int i = 0; i < N; i++)
{
a[i] = cin.nextInt();
sum += a[i];
}
if (sum % N != 0)
{
Console.WriteLine(-1);
}
else
{
ave = sum / N;
for (int i = 0; i < N; i++)
{
if (a[i] < ave)
{
for (int j = i + 1; j < N; j++)
{
if (!isReachable[j - 1])
{
chokudai++;
isReachable[j - 1] = true;
}
if (a[j] > ave)
{
int diff = Math.Min(a[j] - ave, ave - a[i]);
a[j] -= diff;
a[i] += diff;
if (a[i] == ave)
{
break;
}
}
}
}
if (a[i] > ave)
{
for (int j = i + 1; j < N; j++)
{
if (!isReachable[j - 1])
{
chokudai++;
isReachable[j - 1] = true;
}
if (a[j] < ave)
{
int diff = Math.Min(ave - a[j], a[i] - ave);
a[j] += diff;
a[i] -= diff;
if (a[i] == ave)
{
break;
}
}
}
}
}
Console.WriteLine(chokudai);
}
}
private Typical90()
{
cin = new Scanner();
}
static void Main()
{
using var cin = new Scanner();
var(n, m) = cin.Int2();
var s = new string[n];
for (int i = 0; i < n; i++)
{
s[i] = cin.Next();
}
int num = n * m + 2;
int si = n * m;
int ti = n * m + 1;
var flow = new MFGraphInt(num);
for (int i = 0; i < n; i++)
{
for (int j = 0; j < m; j++)
{
if (s[i][j] == '#')
{
continue;
}
int k = i * m + j;
if ((i + j) % 2 == 0)
{
flow.AddEdge(si, k, 1);
Helper.DoAt4(i, j, n, m, (ii, jj) => {
if (s[ii][jj] == '.')
{
int kk = ii * m + jj;
flow.AddEdge(k, kk, 1);
}
});
}
else
{
flow.AddEdge(k, ti, 1);
}
}
}
long maxFlow = flow.Flow(si, ti);
Console.WriteLine(maxFlow);
var ans = new char[n][];
for (int i = 0; i < n; i++)
{
ans[i] = new char[m];
}
for (int i = 0; i < n; i++)
{
for (int j = 0; j < m; j++)
{
ans[i][j] = s[i][j];
}
}
var edges = flow.Edges();
foreach (var e in edges)
{
if (e.From == si || e.To == ti || e.Flow == 0)
{
continue;
}
int i0 = e.From / m;
int j0 = e.From % m;
int i1 = e.To / m;
int j1 = e.To % m;
if (i0 == i1 + 1)
{
ans[i1][j1] = 'v';
ans[i0][j0] = '^';
}
else if (j0 == j1 + 1)
{
ans[i1][j1] = '>';
ans[i0][j0] = '<';
}
else if (i0 == i1 - 1)
{
ans[i0][j0] = 'v';
ans[i1][j1] = '^';
}
else
{
ans[i0][j0] = '>';
ans[i1][j1] = '<';
}
}
for (int i = 0; i < n; i++)
{
Console.WriteLine(new string(ans[i]));
}
}
void solve()
{
cin = new Scanner();
N = cin.nextInt();
M = cin.nextInt();
X = cin.nextInt();
Y = cin.nextInt();
a = new int[N];
b = new int[M];
for (int i = 0; i < N; i++)
{
a[i] = cin.nextInt();
}
for (int i = 0; i < M; i++)
{
b[i] = cin.nextInt();
}
bool isA = false;
int curA = 1;
int curB = 0;
int chokudai = a[0] + X;
int ans = 0;
while (true)
{
//Console.WriteLine((isA?"A":"B")+chokudai);
if (isA)
{
if (chokudai <= a[curA])
{
isA = false;
chokudai = a[curA] + X;
//curA++;
}
else
{
curA++;
}
}
else
{
if (chokudai <= b[curB])
{
isA = true;
chokudai = b[curB] + Y;
//curB++;
ans++;
}
else
{
curB++;
}
}
if (curA == a.Length || curB == b.Length)
{
break;
}
}
Console.WriteLine(ans);
}