const std = @import("std");
const BYTES: []u8 = undefined;

pub fn main() !void {
  const stdout = &(try std.io.getStdOut()).outStream().stream;
  const allocator = &std.heap.FixedBufferAllocator.init(BYTES).allocator;

  var result: i32 = 0;

  while(true) {
    var line_buf: [20]u8 = undefined;

    const line = std.io.readLineSlice(line_buf[0..]) catch |err| switch (err) {
      error.OutOfMemory => {
        try stdout.print("Input too long.\n");
        continue;
      },
      error.EndOfStream => {break;},
      else => return err,
    };

    result += std.fmt.parseInt(i32, line, 10) catch {
      try stdout.print("Invalid number.\n");
      continue;
    };
  }

  try stdout.print("{}\n", result);
}