#include <stdio.h>

#include <stdlib.h>

#define SZ 10010

int min(int x, int y)

{

    if(x < y) return x;

    else return y;

}

int main()

{

    int M,N;

    scanf("%d %d",&N,&M);

    int x[SZ],y[SZ];

    int i,j, ans = 1e9, tmp = ;

    for(i=; i<N; i++)

        scanf("%d",&x[i]);

    for(j=; j<M; j++)

        scanf("%d",&y[j]);

    for(i = ; i < N; i++)

    {

        if(x[i] > y[tmp]) break;

        for(j = tmp; j < M; j++)

        {

            if(x[i] < y[j]) break;

        }

        tmp = j - ;

        if(j == ) tmp++, ans = min(ans, y[j] - x[i]);

        else ans = min(ans, min(x[i] - y[j - ], y[j] - x[i]));

        //printf("%d %d %d\n", i, j, ans);

    }

    printf("%d\n", ans);

    return ;

}