//vs2012测试
#include<iostream>
#include<vector>

using namespace std;

#define N 2
#define INF 0x6FFFFFFF

class Solution {
public:
    int maxProfit(vector<int> &prices) 
	{
		if(prices.size()==0)
			return 0;
		int minprices=INF;
		int maxpro=0;
        for(int i=0; i<prices.size(); i++)
		{
			minprices = min(minprices , prices[i]);
			maxpro = max(maxpro, prices[i]-minprices);
		}
		return maxpro;
    }
};

int main()
{
	int a;
	vector<int> prices;
	for(int i=0; i<N; i++)
	{
		cin>>a;
		prices.push_back(a);
	}
	Solution lin;
	cout<<lin.maxProfit(prices)<<endl;
}

//方法一：自测Accepted
#define INF 0x6FFFFFFF
class Solution {
public:
    int maxProfit(vector<int> &prices) {
		if(prices.size()==0)
			return 0;
		int minprices=INF;
		int maxpro=0;
        for(int i=0; i<prices.size(); i++)
		{
			minprices = min(minprices , prices[i]);
			maxpro = max(maxpro, prices[i]-minprices);
		}
		return maxpro;
    }
};