Codeforces Round 980 (Div. 2) Problen A
代码
#include<bits/stdc++.h>
using namespace std;
int main(){
int a,b;
// (b-2x)<=(a-x)
// b-a<=x
int t;
cin>>t;
while(t--){
cin>>a>>b;
if(b<=a)cout<<a<<endl;
else {
int x=b-a;
a-=x;
if(a>0)cout<<a<<endl;
else cout<<0<<endl;
}
}
return 0;
}