void main()
{
    longint n,i,j,sum=0;
    clrscr();
    printf("\n PLEASE ENTER THE VALUE OF N: ");
    scanf("%ld",&n);
    printf("\n SUM = ");
    for(j=1,i=12;j<=n;i=i+20,j++)
    {
        if(j%2==1)
        {
            sum=sum+i;
            if(j==n)
            printf("%ld",i);
            else
            printf("%ld - ",i);
        }
        else
        {
            sum=sum-i;
            if(j==n)
            printf("%ld",i);
            else
            printf("%ld + ",i);
         }
     }
     printf("\n\n THE SUM IS %ld",sum);

     getch();
}



**************************** OUTPUT *********************************



 PLEASE ENTER THE VALUE OF N: 9

 SUM = 12 - 32 + 52 - 72 + 92 - 112 + 132 - 152 + 172

 THE SUM IS 92



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