COI Secret Word

/*
    Task    : _example
    Author  : Phumipat C. [MAGCARI]
    Language: C++
    Created : 01 February 2023 [21:22]
*/
#include<bits/stdc++.h>
using namespace std;
char a[1000010],b[1000010];
int kmp[1000010];
char ans[1000010];
int jump[1000010];
int main(){
    int q;
    scanf("%d",&q);
    while(q--){
        scanf(" %s %s",a+1,b+1);
        int lena=strlen(a+1),lenb=strlen(b+1);
        int j=0;
        for(int i=2;i<=lenb;i++){
            while(j>0 && b[j+1]!=b[i])  j=kmp[j];
            if(b[j+1]==b[i])    j++;
            kmp[i]=j;
        }
        j=0;
        int idx=0;
        for(int i=1;i<=lena;i++){
            while(j>0 && b[j+1]!=a[i])  j=kmp[j];
            if(b[j+1]==a[i])    j++;
            ans[++idx] = a[i];
            jump[idx] = j;
            if(j == lenb){
                idx-=lenb;
                j = jump[idx];
            }
        }
        ans[idx+1] = '\0';
        if(idx == 0)    printf("No COI Secret Code\n");
        else            printf("%s\n",ans+1);
    }
    return 0;
}