Count the Operations

In a class, Ania wrote a program that does some work for all integers from 0 to $n - 1$:

for (int i = 0; i < n; i++) {
    work (i);
}

The teacher Petia looked at the program and said it would take too long, since the maximum value of $n$ is $10^{9}$.

So Ania decided to do the work for only some of the numbers. Her new program is:

for (int i = 0; i < n; i++) {
    if (i == x_1) i = y_1;
    if (i == x_2) i = y_2;
    ...
    if (i == x_k) i = y_k;
    work (i);
}

Count how many operations this program performs for a given $n$, and determine whether it terminates. The counted operations are assignments (i = 0, i++, i = y\_1, ...), comparisons (i < n, i == x\_1, ...), and the work itself (work (i)).

The input contains Ania's program, formatted exactly as in the examples. The opening curly bracket is on the line with for, there is a space before every opening round bracket, and the indentation is four spaces. No line ends with a space.

The number of lines with conditionals is $k$, where $0 \le k \le 10^{5}$. The constraints on the values are $0 \le x_i, y_i < n \le 10^{9}$. Other values have no constraints. The line with work appears once, after all the if lines.

Print the number of operations the program performs. If the program never terminates, print -1.