#include <cstdio>
int sum = 0, x, y;
int main() {
scanf("%d%d", &x, &y);
if (x > y) {
int t = y;
y = x;
x = t;
}
for (int i = x + 1; i < y; i ++ ) {
if (i % 2) sum += i;
}
printf("%d\n", sum);
return 0;
}