Calculate Sum of Natural Numbers

1#include <stdio.h>
2
3int main() {
4    int n, sum = 0;
5    
6    printf("Enter n: ");
7    scanf("%d", &n);
8    
9    for (int i = 1; i <= n; i++) {
10        sum += i;  // sum = sum + i
11    }
12    
13    printf("Sum of first %d natural numbers = %d\n", n, sum);
14    return 0;
15}

1#include <stdio.h>
2
3int main() {
4    int n, sum;
5    
6    printf("Enter n: ");
7    scanf("%d", &n);
8    
9    // Formula: n(n+1)/2
10    sum = n * (n + 1) / 2;
11    
12    printf("Sum = %d\n", sum);
13    return 0;
14}