rqnoj.zip_动态密码

var f:array [0..1002,0..1002] of longint; i,j,a,b,k,l,n,m,ans,s:longint; function check(a,b,x,y:integer):boolean; var o:longint; t,t1,t2:int64; begin t1:=f[x,y]; t2:=f[a,b]; t:=(t1*t2) mod 1000000007; o:=f[n+1,m+1]-t; if o<0 then o:=o+1000000007; if o=k then exit(true) else exit(false); end; begin read(n,m,k); f[0,1]:=1; for i:=1 to n+1 do for j:=1 to m+1 do f[i,j]:=(f[i-1,j]+f[i,j-1]) mod 1000000007; ans:=0; for i:=1 to n do for j:=1 to m+1 do if check(i,j,n+1-i,m-j+2) then inc(ans); for i:=1 to n+1 do for j:=1 to m do if check(i,j,n-i+2,m-j+1) then inc(ans); s:=(n+1)*m+(m+1)*n; a:=s; b:=ans; while b>0 do begin l:=a mod b; a:=b; b:=l; end; if s=a then writeln(ans div a) else writeln((ans div a),'/',(s div a)); end.