#include<stdio.h>
main()
{
    int i,n,sum=0;
    printf("Enter a number\n");
    scanf("%d",&n);
    for(i=0; i<=n; i++)
    {   sum=sum+i;
    }

    printf("Sum is %d\n",sum);
}
     
           
Note: Need to be arranged in compiler after copied
   

 OutPut:

Enter a number 4 Sum is 10