#include<iostream>
using namespace std;
int jsh(int a,int b)
{
int s = 0;
if(a%2==0)
a = a+1;
for(;a<=y;a+=2)
{
s=s+a;
}
return s;
}
int main()
{
int a,b;
cin>>a>>b;
cout<<jsh(a,b);
return 0;
}