Books_My_2

#include <stdio.h>

int      a,
      part,
     start = 1000,
     summa =    0,
     sum   =    0,
      full;

////////////////////////////////////////////////////////////////////
int main()                                                        //
{

    printf("Enter count of books: ");
    scanf ("%d", &a);

    part = a % 7;                                                 //        остаток книг < 7
    full = a / 7;                                                 //  полных серий книг по 7 шт.

    for(int i = 1; i <= 7; i++)
    {
        summa += start;
                 start -= 55;
        if( i == part) sum  = summa;
    }

    printf("Total cost = %d\n", summa * full + sum);

return 0;
}