Refactor several nested if with same else

This is not about an existing piece of code but I'm looking for some pattern that may exist in the case that some nested if perform the same thing in their else statement.

if(condition1(a)) {       
    doSomethingWith1(a);        
    if(condition2(a)) {
        doSomethingWith2(a);
    } else {
        elseFn();
    }    
} else {
    elseFn();
}

The doSomethingWith... functions are changing the value of a, making it complex to have all the condition in one if.

So I'm just wondering if there is a clearer way to write it (in C, if possible).

Thanks guys