#include<bits/stdc++.h>
#pragma GCC optimize(2)
using namespace std;
int fa[200005], siz[200005], flg[200005], a[100005], n, m;
long long ans;
inline int g(int p, int q) {
	return (p - 1) * m + q;
}
struct node {
	int h, l, num;
} b[100006];
bool cmp(node p, node q) {
	return p.num < q.num;
}
inline int finds(int p) {
	return (fa[p] == p) ? p : fa[p] = finds(fa[p]);
}
inline void merge(int p, int q) {
	if (siz[p] > siz[q]) {
		fa[q] = p;
		siz[p] += siz[q];
		flg[p] |= flg[q];
	} else {
		fa[p] = q;
		siz[q] += siz[p];
		flg[q] |= flg[p];
	}
}
signed main() {
	ios::sync_with_stdio(0);
	cin.tie(0);
	cout.tie(0);
	cin >> n >> m;
	for (int i = 1; i <= n; i++) {
		for (int j = 1; j <= m; j++) {
			cin >> a[g(i, j)];
			b[g(i, j)] = node{i, j, a[g(i, j)]};
		}
	}
	sort(b + 1, b + n * m + 1, cmp);
	for (int i = 1; i <= n + m; i++) {
		fa[i] = i, siz[i] = 1;
	}
	int u, v;
	for (int i = 1; i <= n * m; i++) {
		u = finds(b[i].h), v = finds(b[i].l + n);
		if (flg[u] && flg[v]) continue;
		if (u == v && flg[u]) continue;
		if (u == v) {
			flg[u] = 1;
			ans += b[i].num;
		} else {
			ans += b[i].num;
			merge(u, v);
		}
	}
	cout << ans;
}