var
	x,m,a,b:int64;
	i:Longint;
	fac:array[0..2001]of int64=(1,437918130,722479105,419467694,390998217,688653593,752369730,314281677,848793393,302778600,641419708,359467170,109119920,291462451,581232364,367552188,19055157,519422664,377413248,184238535,100292593,867553799,680805768,637011622,838031598,954730329,14705621,854687367,82350513,562819783,341406877,11986940,406550952,924707067,697304278,812312671,493805103,750646179,797131515,125408444,593395757,743252791,97269816,625809105,95830437,318440909,191279856,448875092,764072301,941003529,541108809,339617910,981977466,917213110,693389065,939330647,454991628,655104206,938437020,681370120,969117405,153564086,124768900,190510895,380720579,742619942,919179148,860673190,784044468,356858318,849641758,257431766,926581590,488132488,633627778,593920661,234400402,266884017,181686381,657704891,532467852,928162624,121630724,523505981,242416192,940517951,451602922,692382743,856456398,303115999,299200938,638522519,484820571,4950879,652993557,595510479,747441725,565813117,719760882,162603635,531950728,765702160,363728672,790374244,776372982,160226878,217226757,800213188,425234994,877824191,682831525,230335073,830834436,706165316,540595539,144162001,433393698,893091420,997675228,844113510,577889084,874720012,937682696,117557725,705155009,72951350,379968087,950743483,342781022,184481043,153223816,558188636,516225514,438463836,350269020,332366222,493498994,753660595,128078583,238205526,927344283,470091512,192044710,849127063,854869794,502704967,961189336,188562846,643851306,204102562,576865589,574949854,772036106,417276573,773301250,463836195,473281893,894679367,4336597,363467250,317614965,728217456,554126869,874896552,76366192,677000234,337033639,284263197,264056892,538465762,645000912,157420482,14755475,572349905,770650027,208576717,412197753,283971481,892302331,872764474,810673643,764707385,62691675,425317917,827016778,685010988,575309116,86381823,285454093,583163727,483115382,953791654,224496577,413323992,74107909,779820672,988628897,796572345,968946248,444124793,368774859,887671982,535354688,145822049,516927020,988709092,910325210,790606609,425401251,824547428,11347322,841821068,372729338,910253320,383651345,626790213,636443576,633383307,105562610,725643552,766392363,418265499,957763794,832826328,343383160,237604935,582419882,608657845,330910979,511252139,701339131,463738716,849664749,739062237,357088405,324679509,109741460,455887877,269923768,424425198,965651681,471728725,543062503,485378429,571604742,321271335,504455561,509546975,763368909,150072577,232201666,695006444,375079861,765847341,405049322,304181169,685687553,228502082,23642405,733213722,77721395,994809954,217921085,750848255,415201993,877359318,816254961,208800253,165312868,912564763,267878880,620421028,687272398,965091903,910284938,959869931,579283662,460311839,233130006,832629547,806918317,789419725,976360299,66957513,792006720,964835096,764310323,943508794,320822040,855360826,994209082,998710584,451541316,540353405,782850762,83351016,164658610,399153119,484179393,900677914,548996970,540202385,502085905,305629510,414973328,733854511,999551600,929723194,856256948,190437395,831650911,189552007,540085415,264316037,647368479,724859258,63875222,549880942,884378502,48225947,200360748,217411774,428675555,204375967,163813057,11392828,63816753,122454906,279161231,177533667,31612358,140452161,19981188,287350626,225047490,810109242,455285322,682630228,317104780,38098465,981996609,566262664,244205492,11569855,360664468,210352560,808795375,66106220,996704108,52475795,835874618,706698117,834011569,82385442,767403009,260934484,581004588,146951720,315181594,18131026,67347184,660447354,317161158,310293330,957769185,795211642,251210316,376491240,482209772,337887965,715730781,169939932,942501868,896874971,156760010,409840176,442596118,448590113,340183632,448639753,139475086,446619980,683372898,330190835,658072182,120608013,345266529,873204774,859866616,327703544,840550890,500060231,737050414,343707056,929913795,364139378,713522909,605309034,892609044,95663389,422550956,440430257,676836771,616977443,372816409,516450892,308156304,727765485,154582382,122223283,703248501,916757163,626613065,673807982,165855749,104310832,619362396,666635368,551617377,725543210,320014428,83863469,696839568,820486897,690587073,476958860,785342455,964938385,434274056,793377933,473720669,105927603,722446075,463771653,995091580,249784900,362569914,441674995,310891328,443049614,246899301,965628034,8254466,860524980,284046782,649020090,775603661,428599344,313235165,263427830,820210693,584450609,715520777,908274787,449173641,87370462,342675806,667579940,561795065,279679436,78896243,594101806,340351880,104853227,138938342,130890251,986495418,544733609,4904868,918156620,404489692,770967340,158370004,816861962,480737664,420524209,65348113,118371296,286699742,510283129,473058849,602863780,673888495,988224796,727422266,795625516,490010237,643547208,665131,419311146,784876961,259406228,321460624,655258314,98643949,707960681,345366515,677618898,819757880,180025997,737935835,405543032,644653663,490584749,69511883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function pow(a,b:int64):int64;
var r:int64;
begin
	if b=0 then pow:=1
	else begin
		r:=pow(a*a mod m,b div 2);
		if b mod 2=1 then r:=r*a mod m;
		pow:=r;
	end;
end;
begin
	read(a,b);
	if(a<b-1)or(a>b+1)then begin
		writeln(0);exit;
	end;
	m:=1000000007;
	x:=fac[a div 100];
	for i:=1 to a mod 100 do begin
		x:=x*(a-i+1)mod m;
	end;
	x:=x*fac[b div 100]mod m;
	for i:=1 to b mod 100 do begin
		x:=x*(b-i+1)mod m;
	end;
	if a=b then x:=x*2 mod m;
	writeln(x);
end.


Measured memory_bytes: 128