Problem:
Score : 100 points

Problem Statement

You are given two integers a and b.
Determine if a+b=15 or a\times b=15 or neither holds.

Note that a+b=15 and a\times b=15 do not hold at the same time.

Constraints

1 \leq a,b \leq 15

All values in input are integers.

Input

Input is given from Standard Input in the following format:

a b

Output

If a+b=15, print +;
if a\times b=15, print *;
if neither holds, print x.

Sample Input 1

4 11

Sample Output 1

+

4+11=15.

Sample Input 2

3 5

Sample Output 2

*

3\times 5=15.

Sample Input 3

1 1

Sample Output 3

x

1+1=2 and 1\times 1=1, neither of which is 15.

Solution in C (Clang 3.8.0) (judge verdict: Accepted)

#include <stdio.h>

#define forN(i, N) for (i = 0; i < N; i++)

char operation(int a, int b, int n);

int main(int argc, char *argv[]) {
  int num[2];
  int i;

  forN(i, 2) scanf("%d", &num[i]);

  char op = operation(num[0], num[1], 15);
  putchar(op);
  return 0;
}

char operation(int a, int b, int n) {
  if (a + b == n) return '+';
  if (a * b == n) return '*';
  return 'x';
}