Dinitz

const long long infi = 1e18;
class dinitz
{
    public:

        struct edge
        {
            int to, rev;
            long long cap, ocap;
            long long flow()
            {
                return max(ocap-cap, 0ll);
            }
        };
        vector<vector<edge>> edg;
        vector<int> level, q, ptr;
        dinitz(int n)
        {
            level = q = ptr = vector<int>(n); edg = vector<vector<edge>>(n);
        }
        void add_edge(int a, int b, long long c, long long r_cap = 0)
        {
            edg[a].push_back({b, (int)edg[b].size(), c, c});
            edg[b].push_back({a, (int)edg[a].size()-1, r_cap, r_cap});
        }
        long long dfs(int v, int t, long long f)
        {
            if(v==t || !f)
            {
                return f;
            }
            for(int& i=ptr[v]; i<(int)edg[v].size(); i++)
            {
                edge& e = edg[v][i];
                if(level[e.to]==level[v]+1)
                {
                    if(long long p = dfs(e.to, t, min(f, e.cap)))
                    {
                        e.cap -= p; edg[e.to][e.rev].cap += p;
                        return p;
                    }
                }
            }
            return 0;
        }
        long long calci(int s, int t)
        {
            long long flow = 0;
            q[0] = s;
            for(int i=0; i<31; i++)
            {
                do
                {
                    level = ptr = vector<int>(q.size());
                    int qi = 0, qe = level[s] = 1;
                    while(qi<qe && !level[t])
                    {
                        int v = q[qi++];
                        for(edge e : edg[v])
                        {
                            if(!level[e.to] && e.cap>>(30-i))
                            {
                                q[qe++] = e.to; level[e.to] = level[v] + 1;
                            }
                        }
                    }
                    while(long long p = dfs(s, t, infi))
                    {
                        flow += p;
                    }
                }
                while(level[t]);
            }
            return flow;
        }
};