#define _CRT_SECURE_NO_WARNINGS #include #include #include #include #include #include #include #define REP(i,a,b) for(i=a;i> N; REP(k,2,N+1) { A[k] = (19*A[k-1] - 12*A[k-2])/4; } printf("%.18lf\n",A[N]); return 0; }