#include <bits/stdc++.h>
using namespace std;
int main() {
  int t;
  long long int a, b, c;
  cin >> t;
  while (t--) {
    cin >> a >> b >> c;
    long long int max_val = (a + c);
    long long int min_val = b;
    if (a + c <= b) {
      cout << 0 << endl;
    } else if (b + c < a) {
      cout << c + 1 << endl;
    } else {
      long long int ans = (max_val - min_val + 1) / 2;
      cout << ans << endl;
    }
  }
}
