c++: array Why do I need two braces when I initialize

Question

when i use C++ array like this:

array<int, 8> test = {
        1,
        2,
        3,
        4,
        5,
        6,
        7,
        8
};

It's easy to understand, but when i use C++ array like this:

    array<pair<int, int>, 8> dirs = {
        {-1, -1},
        {-1, 0},
        {-1, 1},
        {0, -1},
        {0, 1},
        {1, -1},
        {1, 0},
        {1, 1},
};

The compiler will report an error:No viable conversion from 'int' to 'std::pair<int, int>' But it compiled successfully when I use two curly braces:

    array<pair<int, int>, 8> dirs = {{
        {-1, -1},
        {-1, 0},
        {-1, 1},
        {0, -1},
        {0, 1},
        {1, -1},
        {1, 0},
        {1, 1},
}};

I don't understand why i need two curly braces