#include <bits/stdc++.h>
using namespace std;

#define sc( x ) scanf( "%d" , &x )
#define REP( i , n ) for( int i = 0 ; i < n ; i++ )
#define clr( t , val ) memset( t , val , sizeof(t) )

#define all(v)  v.begin() , v.end()
#define pb push_back
#define SZ( v ) ((int)(v).size())

#define mp make_pair
#define fi first
#define se second

#define test() cout << "hola q hace" << endl;
#define DEBUG( x ) cerr <<  #x << "=" << x << endl;
#define DEBUG2( x , y ) cerr << #x << "=" << x << " " << #y << "=" << y << endl;

#define N 200000

typedef long long ll;
typedef pair< int , int > pii;
typedef vector< int > vi;

#define VIZ(e,x) (orig[e] == x? dest[e] : orig[e])
int n,m,fin;
int orig[N], dest[N], pila[N], top = 0;
vi E[N];
int low[N], dfsn[N], part[N], timer;
int ponte[N], bicomp[N], nbicomp;
vi G[ N + 5 ];
int dfsbcc (int u, int p = -1){
    low[u] = dfsn[u] = ++timer;
    int ch = 0;
    for( auto e : E[ u ] ){
        int v = VIZ (e, u);
        if (dfsn[v] == 0){
            pila[top++] = e;
            G[ u ].pb( v );
            dfsbcc (v, u);
            low[u] = min (low[u], low[v]);
            ch++;
            if (low[v] >= dfsn[u]){
                part[u] = 1;
                nbicomp++;
                do{
                    fin = pila[--top];
                    bicomp[fin] = nbicomp;
                }while (fin != e);
            }
            if (low[v] == dfsn[v]) ponte[e] = 1;
        }else if (v!=p && dfsn[v] < dfsn[u]){
            pila[top++] = e;
            low[u] = min (low[u], dfsn[v]);
        }
    }
    return ch;
}
void bcc (){
    REP(i,n) part[i] = dfsn[i] = 0;
    REP(i,m) ponte[i] = 0;
    nbicomp = timer = 0;
    REP(i,n) if (dfsn[i] == 0) part[i] = dfsbcc (i) >= 2;
}

int DP[ N + 5 ];
int MAXI[ N + 5 ];
int dfs( int u , int p = -1 ){
    DP[ u ] = 1;
    for( int v : G[ u ] ) {
        if( v == p ) continue;
        dfs( v , u );
        DP[ u ] += DP[ v ];
        MAXI[ u ] = max( MAXI[ u ] , DP[ v ] );
    }
}
int main(){
    while( sc( n ) == 1 ){
        sc( m );
        REP( i , N ) E[ i ].clear() , G[ i ].clear();
        REP( i , m ){
            int u , v;
            sc( u ) , sc( v );
            u -- , v --;
            orig[ i ] = u;
            dest[ i ] = v;
            E[ u ].pb( i );
            E[ v ].pb( i );
        }
        clr( MAXI , 0 );
        bcc();
        dfs( 0 , -1 );
        int ans = 1 << 30 , ind = -1;
        REP( i , n )
            if( part[ i ] ){
                int cur = max( MAXI[ i ] , max( n - DP[ i ] , 1 ) );
                if( cur < ans ) ans = cur , ind = i;
            }
        if( ind == -1 ) ind = 0;
        printf( "%d\n" , ind + 1 );
    }
}