Code works, but everything it out of order

Question

I have a problem with my code, the code runs but all of the numbers are everywhere.

RainfallToDate.txt :

0.01
 1.74
0.19
0.65
0.50
0.10
0.00
0.02
0.01
0.06
1.57
7.76

averageRainfall.txt:

 2.99
 3.32
 2.04
 1.06
 0.39
 0.09
 0.00
 0.00
 0.23
 0.78
 1.88
 2.12

Here is the code:

#include <iostream>  // for cout
#include <fstream>   // for file I/O
#include <cstdlib>   // for exit()

using namespace std;

int main()
{
ifstream fin;
ofstream fout;
ifstream fin_rainFall("rainfallToDate.txt");
ifstream fin_average("averageRainfall.txt");

if (fin.fail())
{
    cout << "Input file failed to open.\n";
    exit(-1);
}
fout.open("rainfall.txt");
if (fout.fail())
{
    cout << "Output file failed to open.\n";
    exit(-1);
}

fout << "Rainfall for Cupertino: A Comparison\n" << endl;
fout << "Month\tAverage\t 2015\tDeficit\n" << endl;


 for (int i = 1 ; i <= 12 ;i++) { // counts the month from 1-12
    char num[256];
    char num2[256];

    fout<< i << "\t";

    fin_average.getline(num,256);
    fout<<num << "\t";

    fin_rainFall.getline(num2,220);
    fout<<num2<< "\t";

    double a;
    double b;

    while (fin_average >> a && fin_rainFall >> b){
        fout <<"\t" << (a-b) << endl;

    }
}
fin.close();
fout.close();

return 0;

}

I know where my problem is at, and it is at

double a;
double b;

    while (fin_average >> a && fin_rainFall >> b){
        fout <<"\t" << (a-b) << endl;

    }

once I remove this line of code the code runs perfectly but I need this line so that I can subtract the average to the rainfall. Here is a picture of what I am getting.

Picture of what I am getting -

Picture of what I am supposed to have -

I have been working on trying to figure out how to fix this for the past hours and I have yet to figure out what is wrong.

More details: Pretty much my cost is supposed to print out data from two separate "text files" essentially merging them together into a third text file called rainfall.txt, and in there they are to subtract one and another to get the deficit.

Answer 1

The loop should be:

 for (int i = 1 ; i <= 12 ;i++) { // counts the month from 1-12
    double a;
    double b;

    fin_average >> a;
    fin_rainFall >> b;

    fout << i << "\t" <<a <<"\t" << b << "\t" << (a-b) << endl;
}