[INST] Write a program to find biggest rectangular area in histogram./n [/INST]  ###Response: Here's a Python program that can find the biggest rectangular area in a histogram:

```
def max_area_in_histogram(hist):
    stack = []
    max_area = 0
    i = 0
    while i < len(hist):
        if (not stack) or (hist[i] >= hist[stack[-1]]):
            stack.append(i)
            i += 1
        else:
            top = stack.pop()
            area = hist[top] * ((i - stack[-1] - 1) if stack else i)
            max_area = max(max_area, area)
    while stack:
        top = stack.pop()
        area = hist[top] * ((i - stack[-1] - 1) if stack else i)
        max_area = max(max_area, area)
    return max_area
```

This function takes a list of integer values representing the heights of the histogram bars as its only argument, and returns the maximum rectangular area in the histogram. It uses a stack to keep track of the indices of increasing histograph bars, and calculates the area of the rectangle formed by the top of the stack element and the current element. It then updates the max_area if necessary. Finally, it clears the stack to handle any remaining histogram bars, and returns the maximum area it has found.