#include <algorithm>
#include <cstdio>
#include <vector>
#include <cmath>

using namespace std;

pair< int, int > red[ 100001 ];
pair< int, int > blue[ 100001 ];
int N, M;
double sol = 0.0000;

template< class Tip >
Tip sqr ( Tip A ) {
    return A * A;
}

double pitagora ( pair< int, int > A, pair< int, int > B ) {
       return sqrt ( sqr ( abs ( A.first - B.first ) ) + sqr ( abs ( A.second - B.second ) ) );
}

int main() {
    scanf ( "%d", &N );
    for ( int i = 0 ; i < N ; ++i ) {
        scanf ( "%d %d", &red[ i ].first, &red[ i ].second );
    }
    scanf ( "%d", &M );
    for ( int i = 0 ; i < M ; ++i ) {
        scanf ( "%d %d", &blue[ i ].first, &blue[ i ].second );
    }
    for ( int i = 0 ; i < N ; ++i ) {
        for ( int j = 0 ; j < M ; ++j ) {
            sol = max ( pitagora ( red[ i ], blue[ j ] ), sol );
        }
    }
    printf ( "%.3lf\n", sol );
return 0;
}