string 0;

proc LCS(SA, SB, Beg, End);
char SA, SB;
int  Beg, End;
int  APos, BPos, Len;
[Beg(0):= 0;  End(0):= 0;  Len:= 0;
APos:= 0;
while SA(APos) # 0 do
    [BPos:= 0;
    while SB(BPos) # 0 do
        [if SA(APos) = SB(BPos) then
            [Len:= 1;
            while SA(APos+Len) # 0 and SB(BPos+Len) # 0 and
                  SA(APos+Len) = SB(BPos+Len) do Len:= Len+1;
            ];
        if Len > End(0) - Beg(0) then
            [Beg(0):= SA + APos;
            End(0):= Beg(0) + Len;
            Len:= 0;
            ];
        BPos:= BPos+1;
        ];
    APos:= APos+1;
    ];
];

char S1, S2, It;
int  Beg, End;
[S1:= "thisisatest";
 S2:= "testing123testing";
LCS(S1, S2, @Beg, @End);
for It:= Beg to End-1 do
    ChOut(0, It(0));
CrLf(0);
]