#include #define FOR(i, a, b) for (int i = (a); i < (b); ++i) #define REP(i, n) for (int i = 0, i##_len = (n); i < i##_len; ++i) #define REPR(i, n) for (int i = n; i >= 0; i--) #define INF 1145141919 int dy[] = {0, 0, 1, -1}; int dx[] = {1, -1, 0, 0}; int ny, nx; typedef long long int ll; using namespace std; ll gcd(ll a, ll b) { return b ? gcd(b, a % b) : a; } ll lcm(ll m, ll n) { if ((0 == m) || (0 == n)) return 0; return ((m / gcd(m, n)) * n); } ll llpow(ll x, ll y) { ll ans = 1; REP(i, y) ans *= x; return ans; } int ctoi(char c) { if (c >= '0' && c <= '9') { return c - '0'; } return 0; } //////////////////////////////////////////////////////////////////// int main() { int a,b,c,d; cin >> a >> b >> c >> d; int diff1 = b-a+1, diff2 = d-c+1; //cout << diff1 * diff2 << endl; int res=0; if((a