# c# – Read by CSharp console

## Question:

I am starting in the world of programming and I have just solved the following exercise.

``````Ingresar un número y mostrar la suma de los números que lo anteceden.
Al ingresar el 5 me da como resultado el 10
``````

.

As I do so that by console when entering for example `5` , it shows me `1+2+3+4 = 10` , I leave the code that I make.

``````int num, suma = 0;

Console.Write("Ingresa un número:");

for (int i = 0; i < num; i++)

suma = suma + i;

Console.Write("La suma de los números que anteceden a el número: " + num + " es " + suma + ".");
``````

You can do with a for loop, concatenating the value that the loop carries in each turn, the program would be as follows:

``````        Console.Write("Ingresa un número: ");
int suma = 1;

Console.Write("La suma de los números anteriores a " + num + " es: 1");
for (int i = 2; i < num; i++)
{
suma += i; //Para poder mostrar los números desde el uno, ya que i en un inicio va a valer 0
Console.Write(" + " + i);
}
Console.Write(" = " + suma);

The `suma` variable is initialized to 1 for the following reasons:
2) In order to concatenate the "+" signs in each turn, they have to be written at the beginning of each `Console.Write()` within the for loop, so it is necessary to have a number already written beforehand. Let me explain: Before starting the for loop, write the phrase "The sum of the numbers before" + num + "is: 1" since, having that one there, we can concatenate, within the for, at the beginning of each write a plus sign, since we know that before there will always be a number. This helps us so that, at the end of the for loop turns, a plus sign does not appear. If we leave the plus sign at the end of writing the for loop, it would look like this (in the case that num = 5): `1 + 2 + 3 + 4 + = 10`