#include<stdio.h>
int main() 
{
int num,sum=0,i ;
printf("Please, Enter a positive number : "); 
scanf("%d",&num);
if(num<0)
printf("\nYou have Entered a negative number. Please, try again.");
else
{
for(i=1;i<=num;i++)
sum=sum+i;
printf("\nThe sum of upto %d is : %d",num,sum);
} 
return 0;
}