```go
package main

import "fmt"

func main() {
	var t int
	fmt.Scan(&t)
	for i := 0; i < t; i++ {
		var str, in, exp int
		fmt.Scan(&str, &in, &exp)
		k := in + exp - str
		if k < 0 {
			fmt.Println(exp + 1)
		} else {
			minX := k/2 + 1
			if minX > exp {
				fmt.Println(0)
			} else {
				fmt.Println(exp - minX + 1)
			}
		}
	}
}
```