How can i take a screenshot of a full screen game in c++? I know it can be done with directx and i have written a simple code which can take a screenshot of a window but i don't know how to get a HWND of game.
Here is my code.

    #include <d3dx9.h>
    #include <d3dx9tex.h>
    #include <stdio.h>
    
    #pragma comment(lib,"d3d9.lib")
    #pragma comment(lib,"d3dx9.lib")
    
    int main()
    {
        IDirect3DSurface9 *surface;
        IDirect3DDevice9 *g_pd3dDevice;
        IDirect3D9 *g_pD3D;
        D3DDISPLAYMODE d3ddm;
        D3DPRESENT_PARAMETERS d3dpp;
        HWND hWnd = GetConsoleWindow();
    
        if((g_pD3D = Direct3DCreate9(D3D_SDK_VERSION)) == NULL)
        {
            printf("fail 1");
        }
    
        if(FAILED(g_pD3D->GetAdapterDisplayMode(D3DADAPTER_DEFAULT, &d3ddm)))
        {
            printf("fail 2");
        }
    
        ZeroMemory(&d3dpp, sizeof(D3DPRESENT_PARAMETERS));
    
        d3dpp.Windowed = TRUE;
        d3dpp.SwapEffect = D3DSWAPEFFECT_DISCARD;
        d3dpp.BackBufferFormat = d3ddm.Format;
        d3dpp.BackBufferHeight = d3ddm.Height;
        d3dpp.BackBufferWidth = d3ddm.Width;
    
        if(FAILED(g_pD3D->CreateDevice(D3DADAPTER_DEFAULT,
                                       D3DDEVTYPE_HAL, hWnd,
                                       D3DCREATE_SOFTWARE_VERTEXPROCESSING,
                                       &d3dpp, &g_pd3dDevice)))
        {
            printf("fail 3");
        }
        g_pd3dDevice->CreateOffscreenPlainSurface(800, 600, D3DFMT_A8R8G8B8,     D3DPOOL_SCRATCH, &surface, NULL);
        g_pd3dDevice->GetFrontBufferData(0, surface);
        D3DXSaveSurfaceToFile("c:\\tmp\\output.jpg", D3DXIFF_JPG, surface, NULL, NULL);
        surface->Release();
        return 0;
    }

i wont a screenshot of a different game