#include <iostream>
#include <cstdio>
#include <cstring>
#include <algorithm>
#include <cmath>
#include <vector>
using namespace std;

#define LL long long
#define inf 0x3f3f3f3f
#define MP make_pair
#define mxn 24 * 70

int c[mxn];

int f( int h, int m ) {
    return h * 60 + m;
}
int main() {
    int cas;
    scanf( "%d", &cas );
    while( cas-- ) {
        memset( c, 0, sizeof( c ) );
        int n;
        scanf( "%d", &n );
        for( int i = 1; i <= n; ++i ) {
            int x, h, m;
            scanf( "%d %d:%d", &x, &h, &m );
            int t = f( h, m );
            c[t] += x;
            scanf( "%d:%d", &h, &m );
            t = f( h, m );
            c[t] -= x;
        }
        int ans = c[0];
        for( int i = 1; i < mxn; ++i ) {
            c[i] = c[i-1] + c[i];
            ans = max( ans, c[i] );
        }
        printf( "%d\n", ans );
    }
    return 0;
}