Farmer Feb has three fields with potatoes planted in them. He harvested x potatoes from the first field, y potatoes from the second field and is yet to harvest potatoes from the third field. Feb is very superstitious and believes that if the sum of potatoes he harvests from the three fields is a prime number (http://en.wikipedia.org/wiki/Prime_number), he'll make a huge profit. Please help him by calculating for him the minimum number of potatoes that if harvested from the third field will make the sum of potatoes prime. At least one potato should be harvested from the third field.

-----Input-----
The first line of the input contains an integer T denoting the number of test cases. Each of the next T lines contain 2 integers separated by single space: x and y.

-----Output-----
For each test case, output a single line containing the answer.

-----Constraints-----
- 1 ≤ T ≤ 1000
- 1 ≤ x ≤ 1000
- 1 ≤ y ≤ 1000

-----Example-----
Input:
2
1 3
4 3

Output:
1
4

-----Explanation-----

In example case 1: the farmer harvested a potato from the first field and 3 potatoes from the second field. The sum is 4. If he is able to harvest a potato from the third field, that will make the sum 5, which is prime. Hence the answer is 1(he needs one more potato to make the sum of harvested potatoes prime.)

```python

USER_FILENAME = "<user_code>"
import sys, json, builtins
import math, heapq, bisect, itertools, functools, collections, statistics, fractions, decimal, operator, array, random, re, string, os, pathlib
try:
    import resource as _res
except Exception:
    _res = None
from collections import Counter, defaultdict, deque, OrderedDict
from functools import lru_cache, reduce
from itertools import accumulate, permutations, combinations, product
from math import gcd, ceil, floor, sqrt
from decimal import Decimal
try:
    from typing import *
except Exception:
    pass
try:
    sys.setrecursionlimit(1_000_000)
except Exception:
    pass
try:
    import site as _site
    try:
        _sys_sites = _site.getsitepackages() if hasattr(_site, "getsitepackages") else []
        for _p in _sys_sites:
            if _p and _p not in sys.path:
                sys.path.append(_p)
    except Exception:
        pass
    try:
        _usp = _site.getusersitepackages()
        if isinstance(_usp, str):
            _usp = [_usp]
        for _p in _usp:
            if _p and _p not in sys.path:
                sys.path.append(_p)
    except Exception:
        pass
except Exception:
    pass

ns = {"__name__": "__main__"}
for _k, _v in list(globals().items()):
    if not _k.startswith("_"):
        ns[_k] = _v
_CODE = "# cook your dish here\ndef check_prime(num):\n for i in range(2,num):\n\n  if num%i==0:\n   return ('Not Prime')\n\n else:\n  return ('Prime')\n\nt=int(input())\nfor i in range(t):\n n,m=list(map(int,input().split()))\n s=n+m\n if s%2==0:\n  s+=1\n  while check_prime(s)!='Prime':\n   s+=2\n   res= check_prime(s)\n   if res=='Prime':\n    print(s-n-m)\n    break\n  else:\n   print(s-n-m)\n else:\n\n  while True :\n   s += 2\n   res = check_prime(s)\n   if res == 'Prime':\n    print(s-n-m)\n    break\n\n"
_co = compile(_CODE, USER_FILENAME, "exec")
exec(_co, ns, ns)

```

Measured memory_bytes: 13361