Write a C program to find the sum of first n natural numbers

Description: Take a number n as input. Print the sum of numbers from 1 to n.

Hint:

• Keep a variable sum = 0 and add each number to it in a loop.

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C program to find the sum of natural numbers

#include <stdio.h>

int main(void) {
    int n, sum = 0;

    printf("Enter n: ");
    scanf("%d", &n);

    for (int i = 1; i <= n; i++) {
        sum += i;
    }
    printf("Sum of 1 to %d = %d\n", n, sum);
    return 0;
}

Output:

How it works

• The loop adds 1, 2, 3 … up to n into sum.
• There is also a formula: n * (n + 1) / 2, which gives 55 for n = 10 without a loop.

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