1 #include<bits/stdc++.h>
  2 #define IOS ios::sync_with_stdio(false);//不可再使用scanf printf
  3 #define Max(a, b) ((a) > (b) ? (a) : (b))//禁用于函数，会超时
  4 #define Min(a, b) ((a) < (b) ? (a) : (b))
  5 #define Mem(a) memset(a, 0, sizeof(a))
  6 #define Dis(x, y, x1, y1) ((x - x1) * (x - x1) + (y - y1) * (y - y1))
  7 #define MID(l, r) ((l) + ((r) - (l)) / 2)
  8 #define lson ((o)<<1)
  9 #define rson ((o)<<1|1)
 10 #define Accepted 0
 11 #pragma comment(linker, "/STACK:102400000,102400000")//栈外挂
 12 using namespace std;
 13 inline int read()
 14 {
 15     int x=0,f=1;char ch=getchar();
 16     while (ch<'0'||ch>'9'){if (ch=='-') f=-1;ch=getchar();}
 17     while (ch>='0'&&ch<='9'){x=x*10+ch-'0';ch=getchar();}
 18     return x*f;
 19 }
 20 typedef long long ll;
 21 const int maxn = 2000 + 10;
 22 const int MOD = 1000000007;//const引用更快，宏定义也更快
 23 const int INF = 1e9 + 7;
 24 const double eps = 1e-6;
 25
 26 struct edge
 27 {
 28     int u, v, c, f;
 29     edge(int u, int v, int c, int f):u(u), v(v), c(c), f(f){}
 30 };
 31 vector<edge>e;
 32 vector<int>G[maxn];
 33 int level[maxn];//BFS分层，表示每个点的层数
 34 int iter[maxn];//当前弧优化
 35 int m;
 36 void addedge(int u, int v, int c)
 37 {
 38     e.push_back(edge(u, v, c, 0));
 39     e.push_back(edge(v, u, 0, 0));
 40     m = e.size();
 41     G[u].push_back(m - 2);
 42     G[v].push_back(m - 1);
 43 }
 44 void BFS(int s)//预处理出level数组
 45 //直接BFS到每个点
 46 {
 47     memset(level, -1, sizeof(level));
 48     queue<int>q;
 49     level[s] = 0;
 50     q.push(s);
 51     while(!q.empty())
 52     {
 53         int u = q.front();
 54         q.pop();
 55         for(int v = 0; v < G[u].size(); v++)
 56         {
 57             edge& now = e[G[u][v]];
 58             if(now.c > now.f && level[now.v] < 0)
 59             {
 60                 level[now.v] = level[u] + 1;
 61                 q.push(now.v);
 62             }
 63         }
 64     }
 65 }
 66 int dfs(int u, int t, int f)//DFS寻找增广路
 67 {
 68     if(u == t)return f;//已经到达源点，返回流量f
 69     for(int &v = iter[u]; v < G[u].size(); v++)
 70         //这里用iter数组表示每个点目前的弧，这是为了防止在一次寻找增广路的时候，对一些边多次遍历
 71         //在每次找增广路的时候，数组要清空
 72     {
 73         edge &now = e[G[u][v]];
 74         if(now.c - now.f > 0 && level[u] < level[now.v])
 75             //now.c - now.f > 0表示这条路还未满
 76             //level[u] < level[now.v]表示这条路是最短路，一定到达下一层，这就是Dinic算法的思想
 77         {
 78             int d = dfs(now.v, t, min(f, now.c - now.f));
 79             if(d > 0)
 80             {
 81                 now.f += d;//正向边流量加d
 82                 e[G[u][v] ^ 1].f -= d;
 83     //反向边减d，此处在存储边的时候两条反向边可以通过^操作直接找到
 84                 return d;
 85             }
 86         }
 87     }
 88     return 0;
 89 }
 90 int Maxflow(int s, int t)
 91 {
 92     int flow = 0;
 93     for(;;)
 94     {
 95         BFS(s);
 96         if(level[t] < 0)return flow;//残余网络中到达不了t，增广路不存在
 97         memset(iter, 0, sizeof(iter));//清空当前弧数组
 98         int f;//记录增广路的可增加的流量
 99         while((f = dfs(s, t, INF)) > 0)
100         {
101             flow += f;
102         }
103     }
104     return flow;
105 }
106 int x[maxn];
107 int main()
108 {
109     int n, m;
110     scanf("%d%d", &n, &m);
111     int s = 0, t = n + 1;
112     for(int i = 1; i <= n; i++)
113     {
114         scanf("%d", &x[i]);
115         if(x[i])addedge(s, i, 1);//所有赞成的与源点连边
116         else addedge(i, t, 1);//所有反对的与汇点连边
117     }
118     while(m--)
119     {
120         int u, v;
121         scanf("%d%d", &u, &v);
122         if(x[u] && !x[v])//u赞成 v反对
123             addedge(u, v, 1);
124         if(x[v] && !x[u])//v赞成 u反对
125             addedge(v, u, 1);//最小割
126     }
127     printf("%d\n", Maxflow(s, t));
128     return Accepted;
129 }