negative_cycle.Floyd

var w:array[1..100,1..100] of longint;
    i,j,n,k:longint;
    negative_cycle:boolean;
function min(a,b:longint):longint;
 begin
  if a < b then min:=a else min:=b;
 end;
Begin
read(n);
for i:=1 to n do
 for j:=1 to n do
  read(w[i][j]);
for k:=1 to n do
 for i:=1 to n do
  for j:=1 to n do
   w[i][j]:=min(w[i][j],w[i][k]+w[k][j]);
for i:=1 to n do if w[i][i] < 0 then negative_cycle:=true;
end.