求解

var
  a,b,s1,s2,s3,s,t,s4,s5,s6,o,k:ansistring;
  p,p1,p2,p3,p4,p5,p6,p7,p8:real;
  u,m,n,i,j:longint;
begin
  readln(a);
  readln(b);
  readln(n);
  repeat
    s1:=s+s1;
    i:=i+1;
    s:=copy(a,i,1);
  until s=':';
  repeat
    s2:=t+s2;
    j:=j+1;
    t:=copy(a,i+j,1);
  until t=':';
  s3:=copy(a,i+j+1,length(a)-i-j);
  val(s1,p1);
  val(s2,p2);
  val(s3,p3);
  p:=p1*3600+p2*60+p3;
  repeat
    s4:=o+s4;
    u:=u+1;
    o:=copy(b,u,1);
  until o=':';
    repeat
    s5:=k+s5;
    m:=m+1;
    k:=copy(b,u+m,1);
  until k=':';
  s6:=copy(b,u+m+1,length(b)-u-m);
  val(s4,p4);
  val(s5,p5);
  val(s6,p6);
  p7:=p4*3600+p5*60+p6;
  p8:=p7-p;
  p8:=p8*n;
  write(p8:0:0);
end.