Language: C++

#include <algorithm>
#include <atcoder/mincostflow.hpp>
#include <bitset>
#include <climits>
#include <cmath>
#include <cstdio>
#include <iomanip>
#include <iostream>
#include <map>
#include <numeric>
#include <queue>
#include <set>
#include <sstream>
#include <stack>
#include <string>
#include <unordered_map>
#include <vector>

#define MOD 1000000007
#define MOD2 998244353
#define int long long
#define double long double
#define EPS 1e-9
//#define PI 3.14159265358979

#define rep(i, n) for (int i = 0; i < (int)(n); i++)

using namespace std;

template < typename T >
ostream &operator<<(ostream &os, const vector< T > &A) {
	for (int i = 0; i < A.size(); i++)
		os << A[i] << " ";
	os << endl;
	return os;
}
template <>
ostream &operator<<(ostream &os, const vector< vector< int > > &A) {
	int N = A.size();
	for (int i = 0; i < N; i++) {
		for (int j = 0; j < A[i].size(); j++)
			os << A[i][j] << " ";
		os << endl;
	}
	return os;
}
template < typename T, typename U >
ostream &operator<<(ostream &os, const pair< T, U > &p) {
	os << "(" << p.first << "," << p.second << ")";
	return os;
}
template < typename T, typename U >
istream &operator>>(istream &is, pair< T, U > &p) {
	is >> p.first >> p.second;
	return is;
}
template < typename T >
istream &operator>>(istream &is, vector< T > &A) {
	rep(i, A.size()) is >> A[i];
	return is;
}

typedef pair< int, int > pii;
typedef long long ll;

struct edge {
	int from, to, d, c, i;
	edge(int _from = 0, int _to = 0, int _d = 0, int _c = 0) {
		from = _from;
		to = _to;
		d = _d;
		c = _c;
	}
	bool operator<(const edge &rhs) const {
		return (d == rhs.d) ? (c < rhs.c) : (d < rhs.d);
	}
};
struct aabb {
	int x1, y1, x2, y2;
	aabb(int x1, int y1, int x2, int y2) : x1(x1), y1(y1), x2(x2), y2(y2) {}
};

typedef vector< edge > edges;
typedef vector< edges > graph;
struct flow {
	int to, cap, rev, cost;
	flow(int to = 0, int cap = 0, int rev = 0, int cost = 0) : to(to), cap(cap), rev(rev), cost(cost) {}
};
typedef vector< vector< flow > > flows;

const int di[4] = {0, -1, 0, 1};
const int dj[4] = {-1, 0, 1, 0};
const int ci[5] = {0, 0, -1, 0, 1};
const int cj[5] = {0, -1, 0, 1, 0};
const ll LINF = LLONG_MAX / 2;
const int INF = INT_MAX / 2;
const double PI = acos(-1);

int pow2(int n) { return 1LL << n; }
template < typename T, typename U >
bool chmin(T &x, const U &y) {
	if (x > y) {
		x = y;
		return true;
	}
	return false;
}
template < typename T, typename U >
bool chmax(T &x, const U &y) {
	if (x < y) {
		x = y;
		return true;
	}
	return false;
}

template < typename A, size_t N, typename T >
void Fill(A (&array)[N], const T &val) {
	fill((T *)array, (T *)(array + N), val);
}
struct initializer {
	initializer() {
		cout << fixed << setprecision(20);
	}
};
initializer _____;
int minCostFlow(flows &F, int s, int t, int f) {
	int res = 0;
	vector< int > h(F.size(), 0);
	vector< int > d(F.size());
	vector< int > prevv(F.size());
	vector< int > preve(F.size());
	while (f > 0) {
		priority_queue< pii, vector< pii >, greater< pii > > q;
		d.assign(F.size(), LINF);
		d[s] = 0;
		q.push(pii(0, s));
		while (!q.empty()) {
			pii p = q.top();
			q.pop();
			int v = p.second;
			if (d[v] < p.first)
				continue;
			rep(i, F[v].size()) {
				flow &f = F[v][i];
				if (f.cap > 0 && d[f.to] > d[v] + f.cost + h[v] - h[f.to]) {
					d[f.to] = d[v] + f.cost + h[v] - h[f.to];
					prevv[f.to] = v;
					preve[f.to] = i;
					q.push(pii(d[f.to], f.to));
				}
			}
		}
		if (d[t] == LINF) {
			return -1;
		}
		rep(v, F.size()) h[v] += d[v];
		int tmp = f;
		for (int v = t; v != s; v = prevv[v]) {
			tmp = min(tmp, F[prevv[v]][preve[v]].cap);
		}
		f -= tmp;
		res += tmp * h[t];
		for (int v = t; v != s; v = prevv[v]) {
			flow &f = F[prevv[v]][preve[v]];
			f.cap -= tmp;
			F[v][f.rev].cap += tmp;
		}
	}
	return res;
}
int N, M, K, T, Q, H, W;
signed main() {
	cin >> N >> M;
	vector< string > S(N);
	cin >> S;
	vector< vector< int > > grid(N, vector< int >(M, 0));
	int k = 1;
	rep(i, N) rep(j, M) {
		if (S[i][j] == '#') {
			grid[i][j] = -1;
		} else if (S[i][j] == 'o') {
			grid[i][j] = k++;
		}
	}
	atcoder::mcf_graph< int, int > F(N * N + k + 2);
	int s = N * N + k, t = s + 1;
	rep(i, N) rep(j, M) if (grid[i][j] > 0) {
		int k = grid[i][j];
		int si = i, sj = j;
		vector< vector< int > > done(N, vector< int >(M, 0));
		queue< pii > q;
		q.emplace(si, sj);
		while (!q.empty()) {
			int i, j;
			tie(i, j) = q.front();
			q.pop();
			F.add_edge(N * M + k - 1, i * M + j, 1, sj - j + si - i);
			if (i + 1 < N && !done[i + 1][j]) {
				done[i + 1][j] = 1;
				q.emplace(i + 1, j);
			}
			if (j + 1 < M && !done[i][j + 1]) {
				done[i][j + 1] = 1;
				q.emplace(i, j + 1);
			}
		}
	}
	rep(i, N) rep(j, M) {
		F.add_edge(i * M + j, t, 1, 0);
	}
	rep(l, k) {
		F.add_edge(s, N * M + l, 1, 0);
	}
	auto ans = F.flow(s, t);
	cout << -ans.second << endl;
	return 0;
}

Compiler output:
a.cc:2:10: fatal error: atcoder/mincostflow.hpp: No such file or directory
    2 | #include <atcoder/mincostflow.hpp>
      |          ^~~~~~~~~~~~~~~~~~~~~~~~~
compilation terminated.