#include <cstdio>
#include <algorithm>
using namespace std;
int main () {
    freopen("chess.in", "r", stdin);
    freopen("chess.out", "w", stdout);
    int a, b, c, d;
    scanf("%d %d %d %d", &a, &b, &c, &d);
    int dx = abs(a - c), dy = (d - b);
    if ( (dx == 1 && dy == 2) || (dx == 2 && dy == 1) || dx == dy || dx == 0 || dy == 0 )
            puts("YES");
        else
            puts("NO");

    return 0;
}