AtCoder Grand Contest 015（Ａ A - A+...+B Problem）

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≤10⁹
• A and B are integers.

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Input

Input is given from Standard Input in the following format:

N A B

Output

Print the number of the different possible sums.

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Sample Input 1

Copy

4 4 6

Sample Output 1

Copy

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.

 

#include <bits/stdc++.h>
#define ll long long
using namespace std;

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