#include<iostream>
#define dx 1000000000
using namespace std;
int main()
{
    int a,b,i,j;
    cin>>a>>b;
    for(i=1;i<=dx;i++)
    {
        a++;
        b++;
        if(a+a==b)
        {
            cout<<i<<"\n";
            return 0;
        }
    }
}