var s1,s:string;
    i,k,x,code:integer;

begin
  read(s);
  i:=2; s1:=s[1]+s[2];
   repeat
    begin
     val(s1,k,code);
     x:=k mod 7;
     str(x,s1); inc(i); s1:=s1+s[i];
    end;
   until i>=length(s);
   if s1<>'' then
    begin
     val(s1,k,code);
     x:=k mod 7;
    end;
   write(x);
end.


very simple

slish, hare vipendrivats9

#include <stdio.h>
#include <string.h>
const int d[6] = {1,3,2,6,4,5};
int main()
{
    char s[50];
    gets(s);
    int sum = 0, n = strlen(s);
    for (int i = n - 1; i >= 0; --i)
        sum += ( s[i] - '0' ) * d[(n-1-i)%6];
    printf("%d", sum%7);
}

Edited by author 02.12.2009 22:02