Read n and print 1 + 2 + ... + n.
What to build
A loop that builds up a total.
Requirements
- Read
n. - Add up the numbers from 1 to
n.
Input
One whole number n, with 1 ≤ n ≤ 100000.
Output
The sum.
Constraints
n can be up to 100000, so the sum needs a long long.
Example
Input:
5
Output:
15
Why it works
The sum of the numbers up to 100000 is about five billion, which does not fit in an int.
Examples
Example 1 · Input
5
Expected output
15
Example 2 · Input
1
Expected output
1
Hints
Hint 1
Start a total at 0 and add i in a for loop from 1 to n.
Hint 2
For n up to 100000 the sum is bigger than an int can hold: use long long.
Solution
Show one correct solution (try it yourself first)
#include <stdio.h>
int main(void) {
int n;
scanf("%d", &n);
long long sum = 0;
for (int i = 1; i <= n; i++) sum += i;
printf("%lld\n", sum);
return 0;
}