Windows Error while running the program

**edited**
i found my thinking in this program is totally wrong (but i still want to know what cause this run error)

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Hey guys, so I was drafting a simple program on miles per gallon.
Disregard this draft, I had a problem when I tried to run the program.

I used Dev c++, and I can compiled the program.

But when I press ctrl + f10 to run the program, it said gallon.exe has encountered a problem....

just like the screenshot i took.

what is the problem? here is my code.

// Miles per gallon program
// Written in C++

#include <iostream>
using namespace std;

int main()
    {
    
    // assign the type
    int gallon,   // gallon used
        miles,    // miles used
        totalMiles,  // total miles driven
        totalGallon; // total gallon used
    float mpg;       // miles per gallon
    
    // initialization
    totalMiles = 0;
    totalGallon = 0;
    mpg = 0;
    
    //formula
    mpg = totalMiles / totalGallon;
    
    // let us get a welcome message first
    cout << "Welcome to Driver Mile Per Gallon Program! A simple and an easy use program to find out mile per gallon for your tankful!\n" <<endl;
    cout << "Please follow the guideline to operate the program properly:\n" <<endl;
    cout << "[1] Enter any positive value for each input.\n" <<endl;
    cout << "[2] Enter -1 to end this program and will print the mile per gallon result at the end of the program.\n" <<endl;
    
    // now let us begin our program
    while (miles && gallon != -1) {
          cout << "Enter the mile driven:\n";
          cin >> miles;
          cout << "Enter the gallon used:\n";
          cin >> gallon;
          totalMiles = totalMiles + miles;
          totalGallon = totalGallon + gallon;
    }
    
    // how to find the mile per gallon
    
    if (miles && gallon != -1) {
    cout << "Your Mile Per Gallon is: " << mpg << "\n";
    }
    else
        cout << "You did not enter any value!\n" <<endl;
    return 0;
    }