---------------------------------------------AC code---------------------------------------------

#include<cstdio>
#include<algorithm>

#ifdef WIN32
#   define outl "%I64d"
#else
#   define outl "%lld"
#endif

using namespace std;

inline int read(){
    int x = 0;
    bool f = 1;
    char ch = getchar();
    while(ch < '0' || ch > '9'){
        if(ch == '-')   f = 0;
        ch = getchar();
    }
    while(ch >= '0' && ch <= '9'){
        x = x * 10 + ch - '0';
        ch = getchar();
    }
    return f ? x : -x;
}

typedef long long LL;
const int MAXN = 100005;
int CASES, n;
LL ans, remain;
struct P{
    int a, b, c;//a:die; b:involve; c:survive;
}p[MAXN];

bool cmp(P x, P y){
    return x.c > y.c;
}

int main(){
//  freopen("army.in", "r", stdin);
//  freopen("army.out", "w", stdout);
    CASES = read();
    while(CASES--){
        n = read();
        for(int i = 1; i <= n; i++) p[i].a = read(), p[i].b = read(), p[i].c = p[i].b - p[i].a;
        sort(p+1, p+n+1, cmp);
        ans = 0, remain = 0;
        for(int i = 1; i <= n; i++){
            if(remain < p[i].b){
                ans += p[i].b - remain;
                remain = (LL)p[i].c;
            }
            else{
                remain -= (LL)p[i].b;
                remain += (LL)p[i].c;
            }
        }
        printf(outl"\n", ans);
    }
    return 0;
}