#include<iostream>
using namespace std;
int main()
{
    int a1, a2, n;
    cin >> a1 >> a2 >> n;
    int d = a2 - a1;
    int an = a1 + (n - 1) * d;
    cout << an << endl;
    return 0;
}

#include<iostream>
using namespace std;
int main(){
	int a,b,n;
	cin>>a>>b>>n;
	cout<<(b-a)*(n-1)+a;
	return 0;
}

#include <iostream>
#include <bits/stdc++.h>
using namespace std;
const int N=1e7+10;
const int INF=0x3f3f3f3f;
int main()
{
	int a,b,z;
	cin>>a>>b>>z;
	int s=b-a;
	for(int i=1;i<=z-2;i++)
	{
		b+=s;
	}
	cout<<b;
}

#include<iostream>
using namespace std;
int main()
{
    int a1, a2, n;
    cin >> a1 >> a2 >> n;
    int d = a2 - a1;
    int an = a1 + (n - 1) * d;
    cout << an << endl;
    return 0;
}

#include<bits/stdc++.h>
#include<cstring>
#include<queue>
#include<set>
#include<stack>
#include<vector>
#define ll long long
using namespace std;
const int N=1e5+10;
const int M=2023;
const int inf=0x3f3f3f3f;
int n,m,k;
int main()
{
	cin>>n>>m>>k;
	cout<<n+(k-1)*abs(m-n);
	return 0;
}

int a,b,n;
cin >> a >> b >> n ;
cout << a +(n - 1) * (b -a) ;

#include <stdio.h>
#include <iostream>
using namespace std;
int main()
{
	int a1,a2,n;
	cin >>a1 >> a2 >> n;
	int ans ;
	ans = a1 + (a2 - a1)*(n-1);
	cout << ans << endl;
}