#include<iostream>
#include<cstdlib>
#include<cstring>
#include<cstdio>
using namespace std;
struct poi{int too,pre;}e[2000001];
int n,x,y,t,tot,ans,num,lin[1000001],last[1000001],v[1000001];
void add(int x,int y){e[++tot].too=y;e[tot].pre=last[x];last[x]=tot;}
bool dfs(int x)
{
    for(int i=last[x],too=e[i].too;i;i=e[i].pre,too=e[i].too)
    if(v[too]!=t)
    {
        v[too]=t;
        if((!lin[too])||dfs(lin[too]))
        {
            lin[too]=x;
            return 1;
        }
    }
    return 0;
}
int main()
{
    scanf("%d",&n);
    for(int i=1;i<=n;i++)scanf("%d %d",&x,&y),add(x,i),add(y,i);
    for(int i=1;i<=10000;i++)
    {
        ++t;
        if(dfs(i))ans++;
        else break;
    }
    printf("%d\n",ans);
}