#include<iostream> using namespace std; int main() { int m,n,s,t; cin>>m>>n; if(m%2==0){ s=m+1; } else{ s=m; } if(n%2==0){ t=n+1; } else{ t=n; } int A=0; while(s<=t){ A+=s; s+=2; } cout<<A; return 0; }