import sys
if sys.subversion[0] == "PyPy":
    import io, atexit
    sys.stdout = io.BytesIO()
    atexit.register(lambda: sys.__stdout__.write(sys.stdout.getvalue()))
 
    sys.stdin = io.BytesIO(sys.stdin.read())
    raw_input = lambda: sys.stdin.readline().rstrip()
 
RS = raw_input
RI = lambda : map(int,RS().split())
RN = lambda : int(RS())
 
''' ...................................................................... '''
 
def search(arr,val,low):
    high = len(arr)-1
    ans = -1
    while low<=high:
        mid = (high+low)/2
        if arr[mid]>=val:
            ans = mid
            high = mid-1
        else:
            low = mid+1
    return ans
 
for _ in xrange(RN()):
    n = RN()
    start,end = [0]*n,[0]*n
    for i in xrange(n):
        start[i],end[i] = RI()
 
    start.sort(); end.sort()
    ans = n
    for i in xrange(n-1):
        k = search(start,end[i]+1,i+1)
        if k!=-1:
            ans = min(ans,k-i-1)
 
    if ans==n: print -1
    else: print ans
 

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

NQo0CjU0IDc3Cjc5IDg0CjIzIDMwCjc4IDgxCjUKOTUgOTUKNzEgOTMKOTkgOTkKODUgODgKNTAgNjAKNQoxNSAzMAo5NSA5OAo4IDgyCjkwIDk0CjQ5IDc4CjYKNDkgNDkKODcgODkKOTIgOTkKNDMgNzgKNjEgNzQKNDAgNDAKOQo2MiA3Nwo4OSA5MAo4NSA5MAo2MCA2Nwo4MSA4Mwo1MSA1Ngo5IDE5Cjc1IDc2CjcgNTk=

5
4
54 77
79 84
23 30
78 81
5
95 95
71 93
99 99
85 88
50 60
5
15 30
95 98
8 82
90 94
49 78
6
49 49
87 89
92 99
43 78
61 74
40 40
9
62 77
89 90
85 90
60 67
81 83
51 56
9 19
75 76
7 59