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