Spiral

#include <cstdio>
#include <iostream>
#include <algorithm>
#include <vector>
#include <string>
#include <queue>
#include <map>
#include <set>
#include <cmath>
#include <sstream>
#include <stack>
#include <cassert>

#define pb push_back
#define mp make_pair
#define PI 3.1415926535897932384626433832795
#define sqr(x) (x)*(x)
#define forn(i, n) for(int i = 0; i < n; ++i)
#define ALL(x) x.begin(), x.end()
#define F first
#define S second
#define m0(x) memset(x,0,sizeof(x))
#define CC(x) cout << (x) << "\n"
#define pw(x) (1ull<<(x)).

using namespace std;
typedef long long ll;
typedef unsigned long long ull;
typedef long double ld;
typedef pair<int,int> pii;
const int INF = 2147483647;
const ll LLINF = 9223372036854775807LL;

ll m,n,i,j;

ll length(ll x) {
  return 2*m+2*n-8*(x-1)-4;
}

int main() {
  freopen("spiral.in", "r", stdin);
  freopen("spiral.out", "w", stdout);

  cin >> m >> n >> i >> j;
  ll level = min(min(i,j), min(m-i+1,n-j+1));
  ll first=(length(1)+length(level-1))*(level-1)/2+1;
  ll second=first+(m-2*(level-1))-1;
  ll third=second+(n-2*(level-1))-1;
  ll fourth=third+(m-2*(level-1))-1;
  if (j==level) CC(first+i-level);
  else if (m-i+1==level) CC(second+j-level);
  else if (n-j+1==level) CC(third+(m-i-level+1));
  else if (i==level) CC(fourth+(n-j-level+1));
  return 0;
}