AtCoder- A+...+B Problem

AtCoder- A+…+B Problem
These N integers belong to the interval [A,B], then the smallest sum of these N numbers may be A+A+…+A+B=(N-1)A+B, the largest It may be A+B+B+…+B=A+(N-1)B, so the possible number is (n-1)*b+a -(n-1)*ab +1

int main()
{
    
    

    cin>>n;

    cin>>a>>b;
    if(a > b || (n <= 1 && a != b) ) {
    
    
        cout<<0;
        return 0;
    }
    cout<<(n-1)*b+a -(n-1)*a-b +1;
    
    
    return 0;
}