c2n2(m):={
local s,ln_,l,n;
s:=size(m);
if (irem(s,2)==1){
m:=append(m,"F");
s:=s+1;
}
ln_:=[];
l:=asc(m);
for (k:=0;k<s;k:=k+2){
n:=l[k]*26+l[k+1];
ln_:=append(ln_,n);
}
return(ln_);
};
n2c2(l):={
local s,n,m;
s:=size(l);
m:="";
for (k:=0;k<s;k++){
n:=l[k];
m:=append(m,char(iquo(n,26)+65));
m:=append(m,char(irem(n,26)+65));
}
return(m);
};
affin2(a,b,l):={
local s;
s:=size(l);
for (k:=0;k<s;k++){
l[k]:=irem(a*l[k]+b,676);
}
return(l);
};
cesar2(a,b,m):={
return(n2c2(affin2(a,b,c2n2(m))));
};