func_code_string: #include <bits/stdc++.h>   using namespace std;   const int N = 2e5 + 5;   const int M = 2e3 + 50;   const int INF = 0x7fffffff;   const int mod = 1e9 + 7;   const int sz = 18;   const double eps = 1e-10;   const double pi = acos(-1);   long long n, m;   char str[N];   int f[N];   template <class T>   inline void read(T &x) {     char c;     x = 1;     while ((c = getchar()) <  0  || c >  9 )       if (c ==  - ) x = -1;     T res = c -  0 ;     while ((c = getchar()) >=  0  && c <=  9 ) res = res * 10 + c -  0 ;     x *= res;   }   int main() {     int t;     read(t);     while (t--) {       read(n);       read(m);       long long l, r;       for (int i = 1; i <= n; i++) {         long long tmp = 1ll * i * (i - 1) / 2;         if (tmp >= m) {           l = i;           break;         }       }       r = (l - 1) - ((l - 1) * l / 2 - m);       l = n - l + 1;       r = n - r + 1;       for (int i = 1; i <= n; i++) {         if (i == l || i == r)           cout <<  b ;         else           cout <<  a ;       }       cout << endl;     }     return 0;   }   