<p>Given an array of integers arr, find the sum of <code>min(b)</code>, where <code>b</code> ranges over every (contiguous) subarray of <code>arr</code>. Since the answer may be large, return the answer <strong>modulo</strong> <code>10<sup>9</sup> + 7</code>.</p>

<p>&nbsp;</p>
<p><strong class="example">Example 1:</strong></p>

<pre>
<strong>Input:</strong> arr = [3,1,2,4]
<strong>Output:</strong> 17
<strong>Explanation:</strong> 
Subarrays are [3], [1], [2], [4], [3,1], [1,2], [2,4], [3,1,2], [1,2,4], [3,1,2,4]. 
Minimums are 3, 1, 2, 4, 1, 1, 2, 1, 1, 1.
Sum is 17.
</pre>

<p><strong class="example">Example 2:</strong></p>

<pre>
<strong>Input:</strong> arr = [11,81,94,43,3]
<strong>Output:</strong> 444
</pre>

<p>&nbsp;</p>
<p><strong>Constraints:</strong></p>

<ul>
	<li><code>1 &lt;= arr.length &lt;= 3 * 10<sup>4</sup></code></li>
	<li><code>1 &lt;= arr[i] &lt;= 3 * 10<sup>4</sup></code></li>
</ul>

class Solution:

    def findNse(self,arr):
        stack=[] 
        nse=[0] * len(arr)

        for i in range(len(arr)-1,-1,-1):
            while (len(stack)!=0 and arr[stack[-1]] >= arr[i]):
                stack.pop()
            
            if len(stack)==0:
                nse[i] = len(arr)
            else:
                nse[i]= stack[-1]
            stack.append(i)
        return nse
    
    def findPse(self,arr):
        stack=[]
        pse=[0] * len(arr)

        for i in range(len(arr)):
            while (len(stack)!=0 and arr[stack[-1]]>arr[i]):
                stack.pop()
            
            if len(stack)==0:
                pse[i] = -1
            else:
                pse[i]= stack[-1]

            stack.append(i)

        return pse

    def sumSubarrayMins(self, arr: List[int]) -> int:
        nse = self.findNse(arr)
        pse = self.findPse(arr)
        print(nse)
        print(pse)
        subArrayMinSum = 0

        for i in range(len(arr)):
            left = i - pse[i]
            right = nse[i] - i
            subArrayMinSum += ((left*right) * arr[i]) % (int)(1e9 + 7)
        return subArrayMinSum % (int)(1e9 + 7) 
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