View Compilation Error

0_0_6534215_16214.cpp: In function `int main()':
0_0_6534215_16214.cpp:117: error: `mat' undeclared (first use this function)
0_0_6534215_16214.cpp:117: error: (Each undeclared identifier is reported only once for each function it appears in.)
0_0_6534215_16214.cpp:117: error: expected `;' before "res"