View Compilation Error

0_0_37024983_3090.cpp: In function 'int main()':
0_0_37024983_3090.cpp:20:19: error: 'scanf' was not declared in this scope
     scanf("%d", &t);
                   ^
0_0_37024983_3090.cpp:27:14: error: 'puts' was not declared in this scope
    puts("YES"); continue;
              ^
0_0_37024983_3090.cpp:69:29: error: 'puts' was not declared in this scope
   puts((flag) ? "YES" : "NO");
                             ^