#include <bits/stdc++.h> using namespace std; int main() { int n,m; cin>>n>>m; unsigned long long sum=0; for(int i=1;i<=m;i++){ if(i%2!=0) sum+=pow(n,i); else sum-=pow(n,i); } cout<<fixed<<setpresicion(2)<<sum<<endl; return 0; }