;;; File:  main.scm
;; Author: ymiyamoto
;;
;; Created on Sat Sep 28 20:04:17 2019
;;
(define-syntax read-number
  (syntax-rules ()
    ((_ nums)
     (define-values nums
       (apply values (map string->number (string-split (read-line) #\space)))))))

(define-syntax read-numbers
  (syntax-rules ()
    ((_ as)
     (define as (map string->number (string-split (read-line) #\space))))
    ((_ as n)
     (define as (map (lambda (_) (map string->number (string-split (read-line) #\space))) (iota n))))))

(define-syntax 1+ (syntax-rules () ((_ x) (+ x 1))))

(define-syntax 1- (syntax-rules () ((_ x) (- x 1))))

(define MOD 1000000007)

(define (mod+ a . b)
  (fold (lambda (x acc) (modulo (+ x acc) MOD)) a b))

(define (mod* a . b)
  (fold (lambda (x acc) (modulo (* x acc) MOD)) a b))

(define (make-comb num)
  (define dp (make-vector num -1))
  (define (fact n) (vector-ref dp n))
  (vector-set! dp 0 1)
  (let loop ((i 1))
    (when (< i num)
      (vector-set! dp i (mod* i (vector-ref dp (1- i))))
      (loop (1+ i))))

  (lambda (n k)
    (define factn (fact n))
    (define powk (expt-mod (fact k) (- MOD 2) MOD))
    (define pownk (expt-mod (fact (- n k)) (- MOD 2) MOD))
    (mod* factn powk pownk)))

(define (solve)
  (define comb (make-comb 10000))

  (read-number (a b c))
  (print (apply mod+
		(map (lambda (i)
		       (mod* (comb (- (+ a b c) i 2) (- c 1))
			     (comb (- (+ a b) i 1) (- b 1))
			     (1- (expt-mod 2 (- (+ a b c) i 1) MOD))))
		     (iota a 1)))))

(solve)