#include<bits/stdc++.h>
using namespace std;
int main(){
	int n,m,a[20][20]={0},z=0,max,i,j,v=0;
	cin>>n>>m;
	for(i=0;i<n;i++){
		for(j=0;j<m;j++){
			cin>>a[i][j];
		}
	}
	max=a[0][0];
	z=a[0][0];
	for(i=0;i<n;i++){
		for(j=0;j<m;j++){
			if(max>a[i][j]){
				max=a[i][j];
			}else(z<a[i][j]);{
				z=a[i][j];
			}
		}
	}
	v=z-max;
	cout<<v;
}
/**************************************************************
	Problem: 1272
	User: huxuanchen
	Language: C++
	Result: Accepted
	Time:11 ms
	Memory:2072 kb
****************************************************************/