is there a way in C++ to write something like

```
    for(int a1=0; a1<n;a1++)
    { 
        for (int a2 = 0; a2 < m; a2++)
        {
          some stuff
        }

    }

```

in a single loop. I already saw stuff like

```
for(int i =0, int j=0; i<n && j<m; i++,j++)

```

but I want the increments to be independent and not synchronous.