View Compilation Error

0_0_1669323_14347.cpp: In function `int main()':
0_0_1669323_14347.cpp:2: error: `T' undeclared (first use this function)
0_0_1669323_14347.cpp:2: error: (Each undeclared identifier is reported only once for each function it appears in.)
0_0_1669323_14347.cpp:2: error: `buf' undeclared (first use this function)
0_0_1669323_14347.cpp:2: error: `ins' undeclared (first use this function)
0_0_1669323_14347.cpp:2: error: `ans' undeclared (first use this function)
0_0_1669323_14347.cpp:2: error: `pre' undeclared (first use this function)