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OI-codes/AtCoder/ABC242/C/C.cpp

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#include <iostream>
using std::cin;
using std::cout;
const char endl = '\n';
const int mod = 998244353;
int n;
long long f[1000005][10], ans;
int main() {
cin >> n;
if (n == 1) {
cout << 9 << endl;
exit(0);
}
for (int i = 1; i <= 9; i++) {
f[1][i] = 1;
}
for (int i = 2; i <= n; i++) {
for (int j = 1; j <= 9; j++) {
f[i][j] = f[i - 1][j];
if (j > 1) {
f[i][j] += f[i - 1][j - 1];
}
if (j < 9) {
f[i][j] += f[i - 1][j + 1];
}
f[i][j] %= mod;
}
}
for (int i = 0; i <= 9; i++) {
ans += f[n][i];
}
cout << ans % mod << endl;
return 0;
}