#include<bits/stdc++.h>
#define irep(i,l,r) for(int (i) = (l); (i) <= (r); ++(i))
#define drep(i,r,l) for(int (i) = (r); (i) >= (l); --(i))
#define ceil(pp,qq) (((pp)>0)^((qq)>0)?-abs(pp)/abs(qq):(pp)%(qq)?(pp)/(qq)+1:(pp)/(qq))
#define floor(pp,qq) (((pp)>0)^((qq)>0)?-ceil(abs(pp),abs(qq)):(pp)/(qq))
#define ll long long
#define LL __int128
using namespace std;

inline ll read(){
	char ch = getchar();
	ll s = 0; bool w = 0;
	while(!isdigit(ch)){if(ch == '-')w = 1;ch = getchar();}
	while(isdigit(ch))s = (s << 3) + (s << 1) + (ch ^ 48), ch = getchar();
	return w ? - s : s;
}

inline char rc(){
	char ch = getchar();
	while(1){
		if(ch >= 'A' && ch <= 'Z')return ch;
		if(ch >= 'a' && ch <= 'z')return ch;
		ch = getchar();
	}
}

template<class T1, class T2>
T1 min(T1 AA, T2 BB){return AA > BB ? BB : AA;}
template<class T1, class T2>
T1 max(T1 AA, T2 BB){return AA < BB ? BB : AA;}

const int itinf = 1e9;
const ll llinf = 4e18;
const int mod = 1000000007;
const int N = 500009;

void solve(){
	int n = read();
	vector<array<ll, 2>>a(n);
	irep(i, 0, n - 1){
		a[i] = {read(), read()};
	}
	sort(a.begin(), a.end());
	auto p = a.begin(), q = a.end();
	-- q;
	ll ans = 0;
	while(p < q){
		auto [in, c1] = *p;
		auto [out, c2] = *q;
		ans += 1ll * (out - in) * min(c1, c2);
		if(c1 == c2)++ p, -- q;
		else if(c1 > c2)c1 -= c2, *p = {in, c1}, -- q;
		else *q = {out, c2}, ++ p;
	}
	printf("%lld\n", ans);
}

int main(){
	int T = read();
	while(T --){
		solve();
	}
	return 0;
}
/*
50 30 30 30 30 30 30 30
10 10 20 20 20 20
40 20 10 10 10 10
*/