View Compilation Error

0_0_15832394_16423.cpp: In function 'int main()':
0_0_15832394_16423.cpp:4:1: error: '_int64' was not declared in this scope
 _int64 b[21],mul;
 ^
0_0_15832394_16423.cpp:7:1: error: 'b' was not declared in this scope
 b[2]=1;
 ^
0_0_15832394_16423.cpp:14:1: error: 'mul' was not declared in this scope
 mul=1;
 ^