#include<stdlib.h>
#include<stdio.h>

int main ( int argc, char **argv) {
	int i = 1;
	double moy = 0;
	for (i; i < argc; i ++ ) {
		moy += atof(argv[i]);
	}
moy = moy/(i-1); 
printf("%f \n", moy );
return 0;
}