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++14 (GCC 5.4.1) (judge verdict: Wrong Answer)

#include <bits/stdc++.h>
using namespace std;
 
#define rep(i, N) for (int i = 0; i < N; i++)
#define pb push_back
 
typedef long long ll;
typedef pair<ll, int> ll_i;

int main() {
    ll n,m,d;
    cin >> n >> m >> d;
    double tmp = 2.0*(m - 1)*(n - d) / (double)(n*n);
    if (d == 0){
        cout << tmp / 2.0 << endl;
    } else {
        cout << fixed << setprecision(10) << tmp << endl;
    }
	return 0;
}