#include <bits/stdc++.h>
using namespace std;
int main() {
  long long t, s, n, e;
  cin >> t;
  for (int i = 0; i < t; i++) {
    cin >> s >> n >> e;
    long long l = 0, r = e + 1, m;
    if (e == 0) {
      if (s > n)
        cout << 1 << endl;
      else
        cout << 0 << endl;
      continue;
    }
    while (r - l > 1) {
      m = (r + l) / 2;
      if (n + m < s + e - m) {
        l = m;
      } else
        r = m;
    }
    if (n < s + e) l++;
    cout << l << endl;
  }
}
