include <stdio.h>

int main() {

int a, b, c, d, e;
scanf("%d", &a);
e = a % 10;
a = a / 10;
d = a % 10;
a = a / 10;
c = a % 10;
a = a / 10;
b = a % 10;

if (e + c == d + b) {
	printf("YES");

} else {

	printf("NO");
}

return 0;

}