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

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        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; }