cf 453A.Little Pony and Expected Maximum

 1 #include<bits/stdc++.h>
 2 #define LL long long
 3 #define LD long double  
 4 #define  N 100005
 5 using namespace std;
 6 inline int ra()
 7 {
 8     int x=0,f=1; char ch=getchar();
 9     while (ch<‘0‘ || ch>‘9‘) {if (ch==‘-‘) f=-1; ch=getchar();}
10     while (ch>=‘0‘ && ch<=‘9‘) {x=x*10+ch-‘0‘; ch=getchar();}
11     return x*f;
12 }
13 double ksm(double a, int p)
14 {
15     double sum=1;
16     for (;p;p>>=1,a*=a)
17         if (p&1)
18             sum*=a;
19     return sum;
20 }
21 int main()
22 {
23     int n=ra(),m=ra();
24     double ans=0;
25     for (int i=1; i<=n; i++)
26         ans+=(double)i*(ksm((double)i/n,m)-ksm((double)(i-1)/n,m));
27     printf("%.12lf",ans);
28     return 0;
29 }