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class Solution {
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  public int surfaceArea(int[][] grid) {
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    int area = 0;
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    int n = grid.length;
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    for (int i = 0; i < n; i++) {
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      for (int j = 0; j < n; j++) {
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        // Adding the top part of grid
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        if (i == 0) area += grid[i][j];
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        else area += Math.abs(grid[i][j] - grid[i - 1][j]);
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        // Adding the left part of grid
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        if (j == 0) area += grid[i][j];
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        else area += Math.abs(grid[i][j] - grid[i][j - 1]);
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        // Adding bottom part of bottom-most cubes
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        if (i == n - 1) area += grid[i][j];
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        // Adding right part for right-most cubes
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        if (j == n - 1) area += grid[i][j];
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        // Add top and bottom surfaces if there is no hole in grid
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        if (grid[i][j] != 0) area += 2;
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      }
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    }
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    return area;
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  }
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}