In a classroom there are 25 students. Their teacher writes 1 at both ends of the blackboard. The first student adds a 2 in the middle between them; each next student adds the sum of each two adjacent numbers already on the blackboard between them. Hence there are numbers 1, 2, 1 after the 1st student; 1, 3, 2, 3, 1 after the second student; 1, 4, 3, 5, 2, 5, 3, 4, 1 after the third student and so on. Find the sum of all numbers on the blackboard after the twenty-fifth student.