FILE = "input.txt"

def main():
    ranges = []
    for line in open(FILE):
        if line == "\n": break
        ranges.append(line.strip().split("-"))
    ranges = sorted([
        (int(start), int(stop)+1) for (start, stop) in ranges
    ], key=lambda x: x[0])
    condensed = [ranges[0]]
    for r in ranges:
        end = condensed[-1][1]
        if r[0] <= end < r[1]:
            condensed[-1] = (condensed[-1][0], r[1])
        elif end < r[0]:
            condensed.append(r)
    return sum(len(range(r[0], r[1])) for r in condensed)


if __name__ == "__main__":
    print(main())