program BusRevenueCalculation;

var
a, b, c, K, revenue: integer;
trips: integer;

begin
// Ввод данных
writeln('Enter the ticket price for the first station (a): ');
readln(a);
writeln('Enter the ticket price for the second station (b): ');
readln(b);
writeln('Enter the ticket price for the final station (c): ');
readln(c);
writeln('Enter the desired revenue amount (K): ');
readln(K);

trips := 0;
revenue := 0;

// Подсчет выручки
while revenue < K do
begin
trips := trips + 1;
revenue := trips (10a + 20b + (50-30trips)*c);
end;

writeln('The bus should make ', trips, ' trips to reach the desired revenue of ', K, ' rub.');

end.