#include <algorithm>
#include <cstdio>
#include <cstring>
using namespace std;
const int MAXN=1010010,MAXM=2000010;
bool vis[MAXN];
int n,m,cnt,ans,head[MAXN],match[MAXN];
struct edge
{
    int nxt,to;
}e[MAXM];
void AddEdge(int u,int v)
{
    e[++cnt].nxt=head[u];
    e[cnt].to=v;
    head[u]=cnt;
}
void AddEdges(int x,int y,int v)
{
    AddEdge(x,v),AddEdge(y,v);
}
int max3(int a,int b,int c)
{
    return max(max(a,b),c);
}
bool DFS(int u)
{
    for(int i=head[u],v;i;i=e[i].nxt)
        if(!vis[v=e[i].to])
        {
            vis[v]=1;
            if(!match[v] || DFS(match[v]))
            {
                match[u]=v,match[v]=u;
                return 1;
            }
        }
    return 0;
}
void Hungary(void)
{
    for(int i=1;i<=m;++i)
        if(!match[i])
        {
            memset(vis,0,sizeof vis);
            if(DFS(i))
                ++ans;
            else
                break;
        }
    printf("%d\n",ans);
}
int main(int argc,char *argv[])
{
    scanf("%d",&n);
    for(int i=1,x,y;i<=n;++i)
    {
        scanf("%d %d",&x,&y);
        AddEdges(x,y,i+10000);
        m=max3(m,x,y);
    }
    Hungary();
    return 0;
}