#include<bits/stdc++.h>
using namespace std;
int main(){
    int n,v;
    cin>>n>>v;
    int c[15][15];
    for(int i=1;i<=n;i++){
        for(int j=1;j<=v;j++){
            cin>>c[i][j];
        }
    }
    int max=c[1][1],min=c[1][1];
    for(int i=1;i<=n;i++){
        for(int j=1;j<=v;j++){
            if (max < c[i][j]){
                max=c[i][j];
            }
            if (min > c[i][j]){
                min=c[i][j];
            }
        }
    }
    cout<<max-min;
}
/**************************************************************
	Problem: 1272
	User: luyanchen
	Language: C++
	Result: Accepted
	Time:10 ms
	Memory:2072 kb
****************************************************************/