#include #define F first #define S second #define MP make_pair #define pb push_back #define all(a) a.begin(), a.end() #define rall(a) a.rbegin(), a.rend() #define LCM(a, b) (a) / __gcd((a), (b)) * (b) #define CEIL(a, b) (a)/(b)+(((a)%(b))?1:0) #define log_2(a) (log((a)) / log(2)) #define ln '\n' using namespace std; using LL = long long; using ldouble = long double; using P = pair; using LP = pair; static const int INF = INT_MAX; static const LL LINF = LLONG_MAX; static const int MIN = INT_MIN; static const LL LMIN = LLONG_MIN; static const int MOD = 998244353; static const int SIZE = 200005; const int dx[] = {0, -1, 1, 0}; const int dy[] = {-1, 0, 0, 1}; vector Div(LL n) { vector ret; for(LL i = 1; i * i <= n; ++i) { if(n % i == 0) { ret.pb(i); if(i * i != n) ret.pb(n / i); } } sort(all(ret)); return ret; } /* * 繰り返し自乗法 */ //typedef long long LL; LL power( LL x, LL n ) { LL res = 1; if( n > 0 ) { res = power( x, n / 2 ); if( n % 2 == 0 ) res = ( res * res ) % MOD; else res = ( ( ( res * res ) % MOD ) * x ) % MOD; } return res; } int main() { ios::sync_with_stdio(false); cin.tie(0); LL N, L; cin >> N >> L; N -= L - 1; N = max(0ll, N); cout << (power(2ll, N) - 1 + MOD) % MOD << endl; return 0; }