D - 88888888

D - 88888888

https://atcoder.jp/contests/abc357/tasks/abc357_d

 

思路

 

Code

https://atcoder.jp/contests/abc357/submissions/54384091

LL n;LL base = 998244353;LL getlen(LL n){LL cnt = 0;while(n){cnt++;n /= 10;}return cnt;
}LL ksm(LL a, LL b)
{LL t = 1;while (b){if (b & 1) t = t * a % base;a = a * a % base, b >>= 1;}return t;
}int main()
{cin >> n;LL len = getlen(n);
//    cout << len << endl;
LL powsum = 0,powone;if(len==19){powone=((LL)ksm(10,18)%base)*10%base;}else{powone = ksm(10, len);} powone %= base;//    LL powi = 1;
//    for(LL i=0; i<n; i++){
//        if (i == 0){
//            powi = 1;
//        } else {
//            powi *= powone;
//            powi %= base;
//        }
//        
//        powsum += powi;
//        powsum %= base;
//    }
    powsum = (ksm(powone, n)%base -1)%base;powsum = powsum*ksm(powone-1,base-2)%base;LL sum = (n%base)*powsum;sum %= base;cout << sum << endl;return 0;
}