# include <iostream> # include <algorithm> # include <vector> # include <string> # include <set> # include <map> # include <cmath> # include <iomanip> # include <functional> # include <utility> # include <stack> # include <queue> # include <list> # include <bitset> # include <complex> #include<limits.h> #include<unordered_map> #include<unordered_set> #include<deque> #include<cstdio> using namespace std; typedef long long ll; typedef unsigned long long ull; const int N = 1000000; const int mod = 1000000007; const int INF = 1 << 30; #define rep(i,n) for(ll i=(ll)0;i<(ll)n;++i) #define ALL(x) x.begin(),x.end() #define pp pair<ll,ll> #define fi first #define se second #define pb push_back #define fix(n) fixed<<setprecision(n) #define itr vector<ll>::iterator int dx[4] = { 0,1,0,-1 }, dy[4] = { 1,0,-1,0 }; string YN(bool b) { return(b ? "YES" : "NO"); } string yn(bool b) { return(b ? "Yes" : "No"); } ll a, b, c=0; int main() { cin >> a >> b; for (int i = a; i <= b;++i)if ((a + b + i) % 3 == 0)++c; cout << c << endl; return 0; }