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2894.cpp

#include<bits/stdc++.h>
using namespace std;
#define MAXN 1010
vector<int> g[MAXN];
int n, m, mx;
int lvl[MAXN], dp[MAXN], sub[MAXN];

void dfs( int u ){
	dp[u] = 0;
	sub[u] = 1;
	for( int v : g[u] ) {
		if( !lvl[v] ) {
			lvl[v] = lvl[u] + 1;
			dfs( v );
			dp[u] += dp[v];
			sub[u] += sub[v];
		}
		else if( lvl[v] < lvl[u] ) ++dp[u];
		else if( lvl[v] > lvl[u] ) --dp[u];
	}
	--dp[u];
	if( lvl[u] > 1 && !dp[u] ) {
		mx = max( mx, sub[u] );
	}
}

int
main() {
	int T;
	scanf( " %d", &T);
	while( T-- ) {
		int c;
		scanf( " %d%d%d", &n, &m, &c );
		for( int i = 0, u, v ; i < m ; ++i ) {
			scanf( " %d%d", &u, &v );
			g[u].push_back( v );
			g[v].push_back( u );
		}
		lvl[c] = 1;
		dfs( c );
		cout << mx << endl;
		memset( g, 0, sizeof( g ) );
		memset( lvl, 0, sizeof( lvl ) );
		mx = 0 ;
	}
	return 0;
}