C++ :

#include <iostream>
using namespace std;
int main(){
	//freopen("test6.in","r",stdin);
    string a,b;
    int la,lb,ai,bi,c,ans=0;
    cin>>a>>b;
    la=a.size();
    lb=b.size();
    for(int i=0;i<la;i++){
        for(int j=0;j<lb;j++){
            ai=i,bi=j,c=0;
            while(a[ai]==b[bi]&&c<min(la,lb)){
                ai++;bi++;
                c++;
            }
            ans=max(ans,c);
        }
    }
    cout<<ans;
    return 0;
}

Pascal :

var
s,s2:string;
a:array[1..100]of string;
i,j,t,m,h,k,o:integer;
begin
 readln(s);readln(s2);s:=s+s2;
 t:=length(s);
 for i:=1 to t-1 do
 begin
  m:=i+1;
  for j:=1 to m do a[j]:=copy(s,j,t-i);
  for h:=1 to m do
  for k:=1 to m do
  if (a[h]=a[k])and(h<>k) then begin o:=length(a[h]);writeln(o); exit;end;
 end;
end.