const std = @import("std");

const Pair = struct {
    low: i32 = 0,
    high: i32 = 0,
    fn fullyOverlaps(self: *Pair, other: *Pair) bool {
        return (self.low <= other.low and self.high >= other.high) or (self.low >= other.low and self.high <= other.high);
    }
    fn partiallyOverlaps(self: *Pair, other: *Pair) bool {
        return (self.low <= other.high and self.high >= other.low);
    }
};

fn parsei32Guaranteed(str: []const u8) i32 {
    return std.fmt.parseInt(i32, str, 10) catch unreachable;
}

pub fn main() !void {
    var file = try std.fs.cwd().openFile("input.txt", .{});
    defer file.close();

    var a = std.io.bufferedReader(file.reader());
    var readerStream = a.reader();

    var count: i32 = 0;
    var buf: [32]u8 = undefined;
    while (try readerStream.readUntilDelimiterOrEof(&buf, '\n')) |line| {
        var pairStrings = std.mem.split(u8, line, ",");
        var pairs = [_]Pair{ .{}, .{} };
        for (pairs) |*pair| {
            var elements = std.mem.split(u8, pairStrings.next().?, "-");
            pair.low = parsei32Guaranteed(elements.next().?);
            pair.high = parsei32Guaranteed(elements.next().?);
        }
        if (pairs[0].partiallyOverlaps(&pairs[1])) {
            count += 1;
        }
    }

    std.debug.print("{d}\n", .{count});
}