CodeForces 478A----Initial Bet

注意5个数全为0的情况

Description

There are five people playing a game called "Generosity". Each person gives some non-zero number of coinsb as an initial bet. After all players make their bets ofb coins, the following operation is repeated for several times: a coin is passed from one player to some other player.

Your task is to write a program that can, given the number of coins each player has at the end of the game, determine the sizeb of the initial bet or find out that such outcome of the game cannot be obtained for any positive number of coinsb in the initial bet.

Input

The input consists of a single line containing five integers c₁, c₂, c₃, c₄ andc₅ — the number of coins that the first, second, third, fourth and fifth players respectively have at the end of the game (0 ≤ c₁, c₂, c₃, c₄, c₅ ≤ 100).

Output

Print the only line containing a single positive integer b — the number of coins in the initial bet of each player. If there is no such value ofb, then print the only value "-1" (quotes for clarity).

Sample Input

Input

2 5 4 0 4

Output

3

Input

4 5 9 2 1

Output

-1
#include<stdio.h>int main(void){int a,b,c,d,e,s;while(~scanf("%d%d%d%d%d",&a,&b,&c,&d,&e)){s=a+b+c+d+e;if(s==0) printf("-1\n");        else if(s%5==0) printf("%d\n",s/5);else printf("-1\n");}return 0;}