easy project plz

Hi all, first, i hope i am not in the wrong forum, second, if i may not abuse, can anyone make me a program ( i lack of tutorials sadly :( ) that can edit a text file, well, it is a math program, it works like this, i have a text file, each line starts with numbers:
0
1
2
3
4
.
.
.
.
100
101
102
103
104
.
.
.
.
.
1000
1001
1002
1003
..............
and when it come to a certan part the numbers are in a desorder:
1500
1435
1436
1437
1438
.
.
.
.
1700

the program i want can change the first number in the line, well just add an amount to it, a simple amount, because the disorder is like this:

1500
1435
1436
1437
1438
1439
1506

so i need it to add a speciefic amount to a the number from a specific line to a specific line, in this case, if we add 66 from line 1 to line 5 it will correct the mess :)

im sorry if im being a pain in the arsh lol, thnx to ho ever fill my request :)