#include <stdlib.h>
#include <stdio.h>
/*#include <math.h>*/

unsigned numPlaces (unsigned long n) {
	if (n >= 100000000) return 9;
	if (n >= 10000000) return 8;
	if (n >= 1000000) return 7;
	if (n >= 100000) return 6;
	if (n >= 10000) return 5;
	if (n >= 1000) return 4;
	if (n >= 100) return 3;
	if (n >= 10) return 2;
	if (n >= 1) return 1;

	return 0;
}

#define N_SEC 1000000000
int main(int argsc, char ** args){
	unsigned digits;
	unsigned long sec, nsec, sum_sec=0, sum_nsec=0;
	/* first value - dont use - not correct*/
	scanf("%lu %lu",&sec,&nsec);
	printf("0.000000000\n");
	/* proceed with the second and over values ..*/
	while(scanf("%lu %lu",&sec,&nsec)!=EOF){
		sum_sec+=sec;
		sum_nsec+=nsec;

		sum_sec += sum_nsec / N_SEC;
		sum_nsec = sum_nsec % N_SEC;

		printf("%lu.",sum_sec);

		/*digits=9-(floor (log10 (abs (sum_nsec)))+1);*/
		digits = 9 - numPlaces(sum_nsec);
		for (int i=1;i<=digits;i++){
			printf("0");
		}
		printf("%lu\n",sum_nsec);
	}

	return 0;
}