int foo(int n)
    int result, last, i, tmp;
    {
    switch(n/1){
        case 2:
            result = n;
        case 1:
            if(n == 1){
                result = 1;
            }
            break;
        case 4:
            return 3;
        case  5:
            result = 5;
        default:
            last = 1;
            while(i < n){
                tmp = result;
                result  = result + last;
                last = tmp;
                i++;
            }
    }
    return result;
}