#include<iostream> #include<iomanip> #include<math.h> #include<vector> #include<algorithm> #include<set> #include<map> #include<unordered_map> #include<queue> #include<stack> #include<string> #include<bitset> #include<random> #include<time.h> #define MOD 1000000007ll #define INF 1000000000ll #define EPS 1e-10 #define REP(i,m) for(long long i=0; i<(ll)m; i++) #define FOR(i,n,m) for(long long i=n; i<(ll)m; i++) #define DUMP(a) for(long long dump=0; dump<(ll)a.size(); dump++) { cout<<a[dump]; if(dump!=(ll)a.size()-1) cout<<" "; else cout<<endl; } #define ALL(v) v.begin(),v.end() #define UNIQUE(v) sort(v.begin(),v.end()); v.erase(unique(v.begin(),v.end()),v.end()); #define pb push_back using namespace std; typedef long long ll; typedef pair<ll, ll> P; typedef long double ld; int main() { ios::sync_with_stdio(false); cin.tie(0); ll a,b; cin>>a>>b; ll ans=0; FOR(i,a,b+1) { if((a+b+i)%3==0) ans++; } cout<<ans<<endl; }