#include <iostream>
using namespace std;
int main() {
int x, y, r = 0;
cin >> x >> y;
if (x < y) {
for (; x < y; x++) if (x % 2 != 0) r += x;
} else {
for (; y < x; y++) if (y % 2 != 0) r += y;
}
cout << r << endl;
}
//https://pt.stackoverflow.com/q/334198/101
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