#include <iostream>
#include <vector>
#include <algorithm>
#include <functional>
#include <map>
#include <stdio.h>
#include <math.h>
#include <iomanip>
#include <queue>

using namespace std;

typedef long long ll;
typedef unsigned long long ull;
typedef long double lld;

#define rep(i,n) for(int i = 0; i < (n); i++)
#define REP(i,x,n) for(int i = (x); i < (n); i++)
#define pb push_back 
#define eb emplace_back 
#define fi first
#define se second
#define all(x) x.begin() , x.end()
#define vi vector<int>
#define vll vector<ll>
#define vb vector<bool>

const static int INF = 1001001001;
const static ll LINF = 1001001001001001001LL;
const static lld PI = 3.1415926535897932384626L;
const static int MOD = int(1e9) + int(7);
//const static ll MOD = ll(1e9) + ll(7);
//const static int MOD = 998244353;
//const static int MOD = 998244353;
const static int MX = 2020202;

template < typename T > bool chmin (T &a , T b) { if (a > b) { a = b; return true; } else { return false; } }
template < typename T > bool chmax (T &a , T b) { if (a < b) { a = b; return true; } else { return false; } }
ll gcd (ll a , ll b) { if (a < b) swap(a , b); if (a % b == 0) return b; else return gcd (b , a % b); }
ll lcm (ll a , ll b) { return (a / gcd (a , b) * b); }
int keta (ll x) { int ret = 0; while(x) { ret++; x /= 10; } return ret; }
inline int in () { int x; scanf("%d" , &x); return x; }
inline ll lin () { ll x; scanf("%lld" , &x); return x; }
inline string sin () { string s; cin >> s; return s; }

void io_setup () {
    cout << fixed << setprecision(15);
    //cin.tie(0);
    //ios::sync_with_stdio(false);
}

bool is_prime (ll x) {
    if (x == 2 || x == 3 || x == 5 || x == 7) {
        return true;
    }
    for (ll i = 3; i * i <= x; i++) {
        if (x % i == 0) {
            return false;
        }
    }
    return true;
}

vb prime_table(MX , true);
void prime () {
    prime_table[0] = prime_table[1] = false;
    for (int i = 2; i < MX; i++) {
        for(int j = i + i; j < MX; j += i) {
            prime_table[j] = false;
        }
    }
}

ll modpow (ll x , ll p) {
    ll ret = 1;
    while (p > 0) {
        if (p & 1) ret = ret * x % MOD;
        x = x * x % MOD;
        p >>= 1;
    }
    return ret;
}

vector<ll> fact(MX , 0);
vector<ll> factinv(MX , 0);

void calc_fact () {
    fact[0] = 1;
    for (int i = 1; i < MX; i++) fact[i] = 1LL * i * fact[i - 1] % MOD;
    for (int i = 0; i < MX; i++) factinv[i] = modpow(fact[i], MOD - 2);
}

ll nCk (ll n , ll k) {
    return fact[n] * factinv[k] % MOD * factinv[n - k] % MOD;
}

ll modsub (ll a , ll b) {
    if (a >= b) return (a - b) % MOD;
    else return (MOD + a - b) % MOD;
}

/*
//memo
v.erase(unique(all(v)), v.end());
*/

void solve() {
    ll a = lin();
    ll b = lin();
    ll n = lin();
    ll m = lin();
    ll ans , x;
    if(a >= b) {
        x = (a - b) / (1 + n);
        ans = min(a - x , b + x);
    } else {
        x = (b - a) / (1 + m);
        ans = min(a + x , b - x);
    }
    cout << ans << endl;
    return;
}

int main () {
    io_setup();
    //prime();
    //calc_fact();
    solve();
    return 0;
}