4(iv)

#include <stdio.h>
#include <math.h>
int main()
{
    int n, i, count = 0;
    printf("Enter the number: ");
    scanf("%d", &n);
    for (i = 1; i <= n; i++)
        count += i;
    printf("Sum of %dth is %d", n, count);
    return 0;
}