multiply two big number using FFT

/*multiply two big number using FFT */
  typedef complex < double > base ;
  const double PI = 2*acos( 0.0 );

void fft ( vector < base > & a, bool invert ) {
    int n = ( int ) a. size ( ) ;

    for ( int i = 1 , j = 0 ; i < n ; ++ i ) {
        int bit = n >> 1 ;
        for ( ; j >= bit ; bit >>= 1 )
            j -= bit ;
        j += bit ;
        if ( i < j )
            swap ( a [ i ] , a [ j ] ) ;
    }

    for ( int len = 2 ; len <= n ; len <<= 1 ) {
        double ang = 2 * PI / len * ( invert ? - 1 : 1 ) ;
        base wlen ( cos ( ang ) , sin ( ang ) ) ;
        for ( int i = 0 ; i < n ; i += len ) {
            base w ( 1 ) ;
            for ( int j = 0 ; j < len / 2 ; ++ j ) {
                base u = a [ i + j ] ,  v = a [ i + j + len / 2 ] * w ;
                a [ i + j ] = u + v ;
                a [ i + j + len / 2 ] = u - v ;
                w *= wlen ;
            }
        }
    }
    if ( invert )
        for ( int i = 0 ; i < n ; ++ i )
            a [ i ] /= n ;
}

void multiply ( const vector < int > & a, const vector < int > & b, vector < int > & res ) {
    vector < base > fa ( a. begin ( ) , a. end ( ) ) ,  fb ( b. begin ( ) , b. end ( ) ) ;
    size_t n = 1 ;
    while ( n < max ( a. size ( ) , b. size ( ) ) )  n <<= 1 ;
    n <<= 1 ;
    fa. resize ( n ) ,  fb. resize ( n ) ;

    fft ( fa, false ) ,  fft ( fb, false ) ;
    for ( size_t i = 0 ; i < n ; ++ i )
        fa [ i ] *= fb [ i ] ;
    fft ( fa, true ) ;

    res. resize ( n ) ;
    for ( size_t i = 0 ; i < n ; ++ i )
        res [ i ] = int ( fa [ i ] . real ( ) + 0.5 ) ;
        int carry = 0 ;
    for ( size_t i = 0 ; i < n ; ++ i ) {
        res [ i ] += carry ;
        carry = res [ i ] / 10 ;
        res [ i ] %= 10 ;
    }
}

int xx[MAX];char s1[MAX],s2[MAX];

int main(){
   // booster();
    //read("input.txt");
    int t;
    scani(t);
    while(t--){
        vi a,b,res;
        scanf("%s%s",s1,s2);
        int len = strlen(s1);
        for(int i = 0;i<len;i++)a.pb(s1[i]-48);
        len = strlen(s2);
        for(int i = 0;i<len;i++)b.pb(s2[i]-48);
      //  for(auto it : b)cout<<it;cout<<endl;
        reverse(all(a));
        reverse(all(b));
        multiply(a,b,res);
        int indx = 0;
       // for(int i = 0;i<res.size();i++)cout<<res[i];cout<<endl;
        reverse(all(res));
        while(indx<res.size()&&res[indx]==0)indx++;
        vi ans;
        for(int i = res.size()-1;i>=indx;i--)ans.pb(res[i]);
        reverse(all(ans));
        if(ans.size()==0)printf("0");
        else
        for(auto it : ans){
            printf("%d",it);
        }
        puts("");
    }


    return 0;
}