AtCoder Regular Contest 112

A A - B = C

#include <iostream>
using i64 = long long;
i64 sum(const i64 &a, const i64 &b) { 
    return (a + b) * (b - a + 1) / 2;
}

int main() {
    int t;
    std::cin >> t;
    while(t--) {
        i64 l, r;
        std::cin >> l >> r;
        i64 minc = l, maxc = r - l;
        if (minc > maxc) std::cout << 0 << '\n'; //if minimum of c > r - l, there is no such pair
        else std::cout << sum(r - l + 1 - maxc, r - l + 1 - minc) << '\n';
    }
}