View Compilation Error

1057801_0_0_3644.cpp: In function `int main()':
1057801_0_0_3644.cpp:20: error: `t' undeclared (first use this function)
1057801_0_0_3644.cpp:20: error: (Each undeclared identifier is reported only once for each function it appears in.)
1057801_0_0_3644.cpp:21: error: `a' undeclared (first use this function)