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#define M(c) d[c-'A']
char p[30],m[30],d[30],L;
P(l,r){
    if(l>=r)return;
    int I,D=30,i=l-1;
    while(++i<r)if(M(m[i])<D)D=M(m[I=i]);
    P(l,I);P(I+1,r);putchar(m[I]);
}
main(){
    scanf("%s%s",p,m);
    for(L=0;p[L];++L)M(p[L])=L;
    P(0,L);
    return 0;
}
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