Calculator in C++

#include <iostream>
#include <stdio.h>

using namespace std;

int a;
int b;
string math;

int main() {

    cout << "Enter a number: " << endl;
    cin >> a;
    cout << "Enter another number: " << endl;
    cin >> b;
    cout << "Enter method of math (+ - * /)" << endl;
    cin >> math;

    if (math == "+") {
        cout << a + b << endl;
    } else if (math == "-") {
        cout << a - b << endl;
    } else if (math == "*") {
        cout << a * b << endl;
    } else if (math == "/") {
        cout << a / b << endl;
    } else {
        cout << "That is not a valid method of math!" << endl;
    }
    return 0;
}