#include <stdio.h>
#include <time.h>

int main(void)
{
    struct timespec starttime, endtime;

    long number = 1e9;

    // printf() displays the formatted output
    printf("Now summing up all numbers from 1 to %li...\n", number);

    clock_gettime(CLOCK_REALTIME, &starttime);

    // sum up from 1 to number
    long sum = 0;
    for (long i = 1; i <= number; i++) {
      sum += i;
    }

    clock_gettime(CLOCK_REALTIME, &endtime);

    printf("Sum = %li\n", sum);

    double time_spent = (endtime.tv_sec - starttime.tv_sec) + (endtime.tv_nsec - starttime.tv_nsec) / 1e9;
    
    printf("Rune time = %f16.9 s\n", time_spent);
    
    return 0;
}