#include <stdio.h>

int main()
{
    long int i, n, sum;
    sum = 0;
    printf("Enter the last number for the sum of series from 1 to ");
    scanf("%ld", &n);

    for (i = 1; i < n; i++)
    {
        sum = sum + i;
    }

    printf("The sum from 1 to %ld = %ld",n, sum);

    return 0;
}

//......Coded by YASH ALAPURIA