Language: C++

#include <iostream>
#include <vector>
#include <cassert>

using namespace std;
using ll = long long;
constexpr ll INF = numeric_limits<ll>::max() / 100;

class Flow
{
public:
    using T = ll;
    struct Edge {
        Edge(const int from_, const int to_, const int reverse_, const T capacity_, bool is_reverse = false) : from{from_}, to{to_}, reverse{reverse_}, capacity{capacity_}, flow{0}, is_reverse(is_reverse) {}
        int from;
        int to;
        int reverse;
        T capacity;
        T flow;
        bool is_reverse;
    };

    Flow(const int v) : V{v}
    {
        edge.resize(v);
    }
    void addEdge(const int from, const int to, const T capacity)
    {
        edge[from].push_back(Edge{from, to, (int)edge[to].size(), capacity, false});
        edge[to].push_back(Edge{to, from, (int)edge[from].size() - 1, 0, true});
    }

    T FordFulkerson(const int s, const int t)
    {
        vector<bool> checked(V);
        T flow = 0;
        while (true) {
            for (int i = 0; i < V; i++) {
                checked[i] = false;
            }
            const T f = dfs_ff(s, t, INF, checked);
            if (f == 0) {
                break;
            }
            flow += f;
        }
        return flow;
    }

    const int V;
    vector<vector<Edge>> edge;

private:
    T dfs_ff(const int pos, const int t, const T flow, vector<bool>& checked)
    {
        if (pos == t) {
            return flow;
        }
        checked[pos] = true;
        for (auto& e : edge[pos]) {
            if (not checked[e.to]) {
                const T res = e.capacity - e.flow;
                if (res > 0) {
                    const T d = dfs_ff(e.to, t, min(flow, res), checked);
                    if (d > 0) {
                        e.flow += min(d, res);
                        edge[e.to][e.reverse].flow -= min(d, res);
                        return d;
                    }
                }
            }
        }
        return 0;
    }
};

template <typename T>
T gcd(const T a, const T b)
{
    return (b != 0) ? gcd(b, a % b) : a;
}


int main()
{
    while (true) {
        int m, n;
        cin >> m >> n;
        if (m == 0 and n == 0) {
            break;
        }
        Flow flow(m + n + 2);
        vector<ll> b(m);
        for (int i = 0; i < m; i++) {
            flow.addEdge(m + n, i, 1);
            cin >> b[i];
        }
        vector<ll> r(m);
        for (int i = 0; i < n; i++) {
            flow.addEdge(i + m, m + n + 1, 1);
            cin >> r[i];
        }

        for (int i = 0; i < m; i++) {
            for (int j = 0; j < n; j++) {
                if (gcd(b[i], r[j]) > 1) {
                    flow.addEdge(i, m + j, 1);
                }
            }
        }
        cout << flow.FordFulkerson(m + n, m + n + 1) << endl;
    }
    return 0;
}

Compiler output:
a.cc:7:20: error: 'numeric_limits' was not declared in this scope
    7 | constexpr ll INF = numeric_limits<ll>::max() / 100;
      |                    ^~~~~~~~~~~~~~
a.cc:7:37: error: expected primary-expression before '>' token
    7 | constexpr ll INF = numeric_limits<ll>::max() / 100;
      |                                     ^
a.cc:7:43: error: no matching function for call to 'max()'
    7 | constexpr ll INF = numeric_limits<ll>::max() / 100;
      |                                      ~~~~~^~
In file included from /usr/include/c++/14/string:51,
                 from /usr/include/c++/14/bits/locale_classes.h:40,
                 from /usr/include/c++/14/bits/ios_base.h:41,
                 from /usr/include/c++/14/ios:44,
                 from /usr/include/c++/14/ostream:40,
                 from /usr/include/c++/14/iostream:41,
                 from a.cc:1:
/usr/include/c++/14/bits/stl_algobase.h:257:5: note: candidate: 'template<class _Tp> constexpr const _Tp& std::max(const _Tp&, const _Tp&)'
  257 |     max(const _Tp& __a, const _Tp& __b)
      |     ^~~
/usr/include/c++/14/bits/stl_algobase.h:257:5: note:   candidate expects 2 arguments, 0 provided
/usr/include/c++/14/bits/stl_algobase.h:303:5: note: candidate: 'template<class _Tp, class _Compare> constexpr const _Tp& std::max(const _Tp&, const _Tp&, _Compare)'
  303 |     max(const _Tp& __a, const _Tp& __b, _Compare __comp)
      |     ^~~
/usr/include/c++/14/bits/stl_algobase.h:303:5: note:   candidate expects 3 arguments, 0 provided