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Find the count of all possible strings of size n.Each character of the string is either ‘R’, ‘B’ or ‘G’. In the final string there needs to be at least r number of ‘R’, at least b number of ‘B’ and at least g number of ‘G’ (such that r + g + b <= n).

**Example 1:**

**Input**: n = 4, r = 1, g = 1, b = 1
**Output:** 36
**Explanation**: No. of 'R' >= 1,
No. of ‘G’ >= 1, No. of ‘B’ >= 1
and (No. of ‘R’) + (No. of ‘B’)
+ (No. of ‘G’) = n then
following cases are possible:
1. RBGR and its 12 permutation
2. RBGB and its 12 permutation
3. RBGG and its 12 permutation
Hence answer is 36.

**Example 2:**

**Input: **n = 4, r = 2, g = 0, b = 1
**Output: **22
**Explanation**: No. of 'R' >= 2,
No. of ‘G’ >= 0, No. of ‘B’ >= 1
and (No. of ‘R’) + (No. of ‘B’)
+ (No. of ‘G’) <= n then
following cases are possible:
1. RRBR and its 4 permutation
2. RRBG and its 12 permutation
3. RRBB and its 6 permutation
Hence answer is 22.

**Your Task: **

You dont need to read input or print anything. Complete the function **possibleStrings() **which takes n, r, g, b as input parameter and returns the count of number of all possible strings..

**Expected Time Complexity:** O(n^{2})

**Expected Auxiliary Space:** O(n)

**Constraints:**

1<= n <=20

1<= r+b+g <=n

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