Codeforces Round #259 (Div. 2)(二)

You can read about expectation using the following link: http://en.wikipedia.org/wiki/Expected_value

#include
     
      
#include
      
        int main() { int m,n; scanf("%d%d",&m,&n); double ans=0; for(int i=1;i<=m-1;i++) ans+=pow(1.0*i/m,n); printf("%.12lf\n",m-ans); return 0; }