#include <iostream>
using namespace std;
  
int main() {
    int n, m;
    cin >> n >> m;
    int maxApples = -1, minApples = 1000000;
    for (int i = 0; i < n; i++) {
        for (int j = 0; j < m; j++) {
            int apples;
            cin >> apples;
            if (apples > maxApples) {
                maxApples = apples;
            }
            if (apples < minApples) {
                minApples = apples;
            }
        }
    }
    int difference = maxApples - minApples;
    cout << difference;
    return 0;
}
/**************************************************************
	Problem: 1272
	User: lijinkai
	Language: C++
	Result: Accepted
	Time:8 ms
	Memory:2072 kb
****************************************************************/