#include <iostream>
using namespace std;
int main() {
int x, y;
cin >> x >> y;
int left = min(x, y);
int right = max(x, y);
int sum = 0;
for (int i = left + 1; i < right; i++) {
if (i % 2 != 0) {
sum += i;
}
}
cout << sum << endl;
return 0;
}
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