#include <stdio.h>

int main(void)
{
	FILE* fp;
	double a, b;

	fp = fopen("testdata.txt", "r");

	fscanf(fp, "%lf", &a);
	fscanf(fp, "%lf", &b);
	printf("%f\n", (a+b)/2);

	fclose(fp);

	return 0;
}