#include <bits/stdc++.h>
using namespace std;
int main()
{
int t;
cin>>t;
while(t--)
{
int str,inte,exp;
cin>>str>>inte>>exp;
if((inte-str)>=exp)
{ cout<<0<<endl; continue;}
if(str<inte)
{
exp = exp -(inte- str);
str = inte;
}
if((exp+inte)<str)
cout<<exp+1<<endl;
else if((exp+inte) == str)
cout<<exp<<endl;
else if(str == inte)
cout<<ceil(exp*1.0/2)<<endl;
else
{
int temp;
if(exp&1)
{
temp = ceil(inte*1.0/2);
cout<<exp-temp+1<<endl;
}
else
{
temp = floor(inte*1.0/2)+1;
cout<<exp-temp+1<<endl;
}
}
}
return 0;
}
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