#include <bits/stdc++.h>
using namespace std;
int t;
int main() {
  ios_base::sync_with_stdio(0);
  cin.tie(0);
  cout.tie(0);
  cin >> t;
  while (t--) {
    int a, b, c;
    cin >> a >> b >> c;
    if (c == 0) {
      if (a <= b)
        cout << 0 << endl;
      else
        cout << 1 << endl;
      continue;
    } else if (a + c <= b) {
      cout << 0 << endl;
      continue;
    }
    int res;
    if (a == b) {
      res = c / 2;
      if (c % 2 == 1) res++;
    } else if (a > b) {
      if (b + c < a)
        res = c + 1;
      else if (b + c == a)
        res = c;
      else {
        if ((b + c - a) % 2 == 1)
          res = (b + c - a) / 2 + 1 + a - b;
        else
          res = (b + c - a) / 2 + a - b;
      }
    } else {
      if ((a + c - b) % 2 == 1)
        res = (a + c - b) / 2 + 1;
      else
        res = (a + c - b) / 2;
    }
    cout << res << endl;
  }
}
