#include
using namespace std;
int main() {
cout << "A: ";
int a;
cin >> a;
cout << "B: ";
int b;
cin >> b;
if (a > b) swap(a, b);
long long sum = b;
while (a != b) {
sum += a;
++a;
}
cout << "SUM: " << sum << '\n';
}