#include <iostream>
#include <cstring>
#include <algorithm>
#include <queue>
#include <set>
//#define int long long
using namespace std;
typedef long long ll;
const int N = 200 + 10, INF = 1e9 + 10;

int n, m, a[N][N], totr, totc, colr[N][N], colc[N][N];
char g[N][N];
vector<int> rc[N], cc[N], G[N * N];
bool st[N * N];
int match[N * N];
bool find(int u) {
	for(auto v : G[u]) {
		if(st[v]) continue; st[v] = 1;
		if(!match[v] || find(match[v]))
			return match[v] = u, 1;
	}
	return 0;
}

signed main() {
	ios::sync_with_stdio(0), cin.tie(0);
	cin >> n >> m;
	int ans = 0;
	for(int i = 1; i <= n; i ++)
		for(int j = 1; j <= m; j ++) {
			cin >> g[i][j];
			if(isdigit(g[i][j])) rc[i].push_back(j), cc[j].push_back(i), a[i][j] = g[i][j] - '1', ans ++;
			else a[i][j] = -1;
			if(g[i][j] == 'o') ans ++;
		}
	for(int i = 1; i <= n; i ++)	
		a[i][0] = 1, a[i][m + 1] = 3;
	for(int i = 1; i <= m; i ++)	
		a[0][i] = 0, a[n + 1][i] = 1;
	for(int i = 1; i <= n; i ++) rc[i].push_back(0), rc[i].push_back(m + 1), sort(rc[i].begin(), rc[i].end());
	for(int i = 1; i <= m; i ++) cc[i].push_back(0), cc[i].push_back(n + 1), sort(cc[i].begin(), cc[i].end());
	for(int r = 1; r <= n; r ++) {
		for(int j = 1; j < rc[r].size(); j ++) {
			int pa = rc[r][j - 1], pb = rc[r][j];
			if((((pb - pa) ^ (((a[r][pa] ^ a[r][pb]) & 2) >> 1)) & 1) == 0) {
				for(int k = pa + 1; k < pb; k ++)
					if(g[r][k] == '.') ans ++;
			}
			else {
				int cnt = 0, cntx = 0;
				for(int k = pa + 1; k < pb; k ++) {
					if(g[r][k] == 'x') cnt ++, cntx ++;
					if(g[r][k] == '.') cnt ++, ans ++;
				}
				if(cnt == 0) return cout << -1 << '\n', 0;
				if(cntx > 0) continue;
				totr ++;
				for(int k = pa + 1; k < pb; k ++)
					colr[r][k] = totr;
				ans --;
			}
		}
//		cout << r << ' ' << ans << '\n';
	}
	for(int c = 1; c <= m; c ++) {
		for(int j = 1; j < cc[c].size(); j ++) {
			int pa = cc[c][j - 1], pb = cc[c][j];
			if((((pb - pa) ^ ((a[pa][c] ^ a[pb][c]) & 1)) & 1)) {
				int cnt = 0, cntx = 0;
				for(int k = pa + 1; k < pb; k ++) {
					if(g[k][c] == 'x') cnt ++, cntx ++;
					if(g[k][c] == '.') cnt ++;
				}
				if(cnt == 0) return cout << -1 << '\n', 0;
				if(cntx > 0) continue;
				totc ++;
				for(int k = pa + 1; k < pb; k ++)
					colc[k][c] = totc;
				ans --;
			}
		}
	}
	for(int i = 1; i <= n; i ++)
		for(int j = 1; j <= m; j ++)
			if(g[i][j] == '.' && colc[i][j] && colr[i][j])
				G[colr[i][j]].push_back(colc[i][j]);
	for(int i = 1; i <= totr; i ++)
		memset(st, 0, sizeof st), ans += find(i);
	cout << ans << '\n';
	
	return 0;
}