for _ in range(int(input())):
n, k = map(int, input().split())
print(k*(n//k) + (k//2 if n%k >= k//2 else n%k))
#include<bits/stdc++.h>
using namespace std;
int main()
{
int t;
cin>>t;
while(t--)
{
long long n,m;
cin>>n>>m;
cout<<((n/m)*m)+min(n%m,m/2)<<endl;
}
}
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1713D - Tournament Countdown | 33A - What is for dinner |