#include<stdio.h>

int main(void) {
	long long int A, B, N, M,num;
	scanf("%lld %lld %lld %lld", &A, &B, &N, &M);
	if (A > B) {
		num = (A - B) / (N + 1);
		printf("%lld", B + num);
	}else{
		num = (B - A) / (N + 1);
		printf("%lld", A + num);
	}
}