#include<stdio.h>

int main(){
	int a, b;
	scanf("%d %d", &a, &b);
	int tmp = (a+b)/2;
	double res;
	if((a+b)%2 == 1){
        res = tmp + 0.5;
        printf("%.1f", res);
	}else
        printf("%d", tmp);
	return 0;
}