Problem:
Score : 200 points

Problem Statement

Snuke has N integers. Among them, the smallest is A, and the largest is B.
We are interested in the sum of those N integers. How many different possible sums there are?

Constraints

1 ≤ N,A,B ≤ 10^9

A and B are integers.

Input

Input is given from Standard Input in the following format:

N A B

Output

Print the number of the different possible sums.

Sample Input 1

4 4 6

Sample Output 1

5

There are five possible sums: 18=4+4+4+6, 19=4+4+5+6, 20=4+5+5+6, 21=4+5+6+6 and 22=4+6+6+6.

Sample Input 2

5 4 3

Sample Output 2

0

Sample Input 3

1 7 10

Sample Output 3

0

Sample Input 4

1 3 3

Sample Output 4

1

Solution in C++14 (GCC 5.4.1) (judge verdict: Accepted)

#include <bits/stdc++.h>
using namespace std;
using ll = long long;
#define rep(i, n) for (int i = 0; i < (int)(n); i++)

int main() {
  ll n,a,b;
  cin>>n>>a>>b;
  if(n==1&&a!=b){
    cout<<0<<endl;
    return 0;
  }
  if(a>b){
    cout<<0<<endl;
    return 0;
  }
  if(n==2){
    cout<<a+b<<endl;
    return 0;
  }
  ll min_s,max_s;
  min_s=a*(n-1)+b;
  max_s=b*(n-1)+a;
  ll ans=max_s-min_s+1;
  cout<<ans<<endl;
}