#include "bits/stdc++.h"
using namespace std;
#define fastcin {\
    cin.tie(0);\
    ios::sync_with_stdio(false);\
}
#define REP(i, a, b) for(int i = a; i < b; i++)
#define RREP(i, a, b) for(int i = a; i > b; i--)
#define print(x) cout << x << "\n"
#define SORT(a, n) sort(a, a+n);
#define REVERSE(a,n) reverse(a,a+n);
#define VSORT(v) sort(v.begin(), v.end());
#define VREVERSE(v) reverse(v.begin(), v.end());
#define MOD 1000000007
typedef long long ll;

int main() {
    fastcin;
    int A, B, ans;
    cin >> A >> B;
    int d = B - A;
    for(int i = d; i <= d*2; i++) {
        if(!(i%3)) ans++;
    }
    // ans = d/3;
    // if(d%3!=1) ans++;
    print(ans);
    return 0;
}