```/***************************************************
F = m a Program

Write a program that solves for the unknown variable
in the F = m a equation.  The user enters two
variable = value pairs (e.g "m = 10.0 F = 3.5") and
the program writes the unknown variable and its
value ("a = .35" in our example).

***************************************************/
#include <iostream>
using namespace std;

int main()
{

cout << "The F = m a Program" << endl;

// Read first variable/value pair
char var1,c;
double val1;
cout << "Enter <var> = <value> : ";
cin >> var1 >> c >> val1;

// Read second variable/value pair
char var2;
double val2;
cout << "Enter <var> = <value> : ";
cin >> var2 >> c >> val2;

// Decide which variable is missing & solve
if (var1 == 'F')
{   // var1 is F
if (var2 == 'm')
cout << "a = " << val1 / val2 << endl;
else
cout << "m = " << val1 / val2 << endl;
}
else
{
if (var1 == 'm')
{  // var1 is m
if (var2 == 'a')
cout << "F = " << val1 * val2 << endl;
else
cout << "a = " << val2 / val1 << endl;
}
else
{  // var1 is a
if (var2 == 'm')
cout << "F = " << val1 * val2 << endl;
else
cout << "m = " << val2 / val1 << endl;
}
}

return 0;
}

```