#include <iostream> #include <string> #include <algorithm> #include <iomanip> #include <vector> #include <map> #include <cmath> #include <queue> #include <utility> #include <functional> #include <deque> #include <cctype> #include <stack> #include <bitset> #include <set> using namespace std; using ll = long long; typedef unsigned long long ull; typedef pair<ll, ll> P; const ll MOD = 1e9 + 7; const ll INF = 1 << 30; const ll INF2 = 9e18; const double INF3 = 9e14; const int dx[4] = { 1,0,-1,0 }, dy[4] = { 0,1,0,-1 }; const int tx[8] = { -1,0,1,-1,1,-1,0,1 }, ty[8] = { -1,-1,-1,0,0,1,1,1 }; #define ALL(x) (x).begin(),(x).end() #define pb push_back #define fr first #define sc second int main() { int a, b, ans = 0; cin >> a >> b; for (int i = a;i <= b;i++) { if ((a + b + i) % 3 == 0)ans++; } cout << ans << endl; return 0; }