def cavityMap(a):
    for i in range(1,len(a)-1):
        for j in range(1,len(a[i])-1):
            if a[i-1][j]<a[i][j] and a[i+1][j]<a[i][j] and a[i][j-1]<a[i][j] and a[i][j+1]<a[i][j]:
                a[i]=a[i][:j]+"X"+a[i][j+1:]
    return a