#include #include #include #include using namespace std; #define rep(i,n) for(int i=0;i<(n);i++) bool isprime[200000]; //エラトテネス void eratos(int m){ for (int i = 0; i <= m; ++i) isprime[i] = true; isprime[0] = isprime[1] = false; //iを残してiの倍数を消していく for (int i = 2; i <= m; ++i){ if(isprime[i]){ for (int j = 2 * i; j <= m; j += i){ isprime[j] = false; } } } return; } int hashh(int num){ while(num >= 10){ int tmp = 0; while(num >= 10){ tmp += num / 10;//1桁ずつ足していく num %= 10; } tmp += num; num = tmp; } return num; } int main(void){ int k, n; cin >> k >> n; eratos(n); vector p; for (int i = k; i <= n; ++i){ if(isprime[i]){ p.push_back(hashh(i)); } } int ans = 0; for (int l = 0; l < p.size(); ++l){ bool flag[10] = {false}; int tmp = 0; for (int r = l; r < l + 10; ++r){ if(r >= p.size()) break; if(flag[p[r]] == false){ tmp++; flag[p[r]] = true; // printf("r: %d\n", r); } else{ // printf("%d %d\n", l, r); break; } } ans = max(ans, tmp); } printf("%d\n", ans); return 0; }