#include <bits/stdc++.h>
#include<ext/pb_ds/assoc_container.hpp>
#include<ext/pb_ds/tree_policy.hpp>
using namespace __gnu_pbds;
using namespace std;

#ifdef velox
#include "debug.h"
#else
#define dbg(x...)
#endif

#define srt(v) sort(v.begin(),v.end())
#define grtsrt(v) sort(v.begin(),v.end(),greater<ll>())
#define unq(v) v.erase(unique(v.begin(),v.end()),v.end())
#define rev(v) reverse(v.begin(),v.end())
#define set_bits(x) __builtin_popcountll(x)
#define fst_zero(x) 63-__builtin_ctzll(x)
#define lst_zero(x) __builtin_ctzll(x)
#define gcd(x,y) __gcd(x,y)
#define lcm(x,y) ((x/gcd(x,y))*y)
#define YES cout << "YES" << endl
#define NO cout << "NO" << endl
#define ceil(x,y) ((x+y-1)/y)
#define ll unsigned long long
#define pb push_back
#define endl '\n'
#define fx(x) fixed<<setprecision(x)
template <typename T> using pbds = tree<T, null_type, less<T>, rb_tree_tag, tree_order_statistics_node_update>;
const ll MOD = 1e9+7;

void file(){
    #ifdef velox
    freopen("input.txt","r",stdin);
    freopen("output.txt","w",stdout);
    freopen("error.txt","w",stderr);
    #endif
}



void solve(){
    string s; cin >> s;
    ll n; cin >> n;
    ll len=s.size();
    string a="";
    ll x=0;
    for(x; x<len; x++){
        if(s[x]=='+') break;
        a+=s[x];
    }
    string b="";
    x++;
    for(x; x<len; x++){
        if(s[x]=='+') break;
        b+=s[x];
    }

    dbg(a,b);
    ll num1=stoll(a);
    ll num2=stoll(b);
    if(num1>num2) swap(num1,num2);
    if(num1==num2){
        cout << (num1*n) << endl;
        return;
    }

    ll lst = num1+(((num2-num1)*(n-1)));

    ll get = ((lst*(lst+1))/2 ) - ((num1*(num1-1))/2);
    ll gap = (num2-num1);
    
    ll mid_get = (((num2-1)*((num2-1)+1))/2 ) - ((num1*(num1+1))/2);
    dbg(get,lst);
    dbg(num1,lst,mid_get);

    ll hv=gap*(gap-1);
    dbg(hv);
    ll r=n-2;
    ll ele = (mid_get*(n-1))+(hv*((r*(r+1))/2));
    dbg(ele);
    cout << get-ele << endl;


}

int main(){
    // file();
    ios_base::sync_with_stdio(0); cin.tie(0);
    ll t=1;
    // cin >> t;
    while(t--) solve();
    return 0;
}