T7314 yyy的巧克力(钟)

 1 #include<iostream>
 2 #include<cstdio>
 3 #include<cstring>
 4 #include<cmath>
 5 #include<algorithm>
 6 #include<queue>
 7 #include<stack>
 8 #define lli long long 
 9 using namespace std;
10 const int mod=998244353;
11 void read(int &n)
12 {
13     char c='+';int x=0;bool flag=0;
14     while(c<'0'||c>'9'){c=getchar();if(c=='-')flag=1;}
15     while(c>='0'&&c<='9')
16     x=(x<<1)+(x<<3)+c-48,c=getchar();
17     flag==1?n=-x:n=x;
18 }
19 lli n,m;
20 int fastmul(int x,int p)
21 {
22     int now=x;
23     int ans=0;
24     while(p)
25     {
26         if(p&1)
27         {
28             --p;
29             ans=(ans+now)%mod;
30         }
31         p>>=1;
32         now=(now+now)%mod;
33     }
34     return (ans-1)%mod;
35 }
36 int main()
37 {
38 //    freopen("bpmp.in","r",stdin);
39 //    freopen("bpmp.out","w",stdout);
40     //read(n);read(m);
41     cin>>n>>m;
42     cout<<fastmul(n,m)%mod;
43     return 0;
44 }