View Compilation Error

0_0_31307303_22627.cpp: In function 'void program()':
0_0_31307303_22627.cpp:262:16: error: could not convert 'solve()' from 'void' to 'bool'
     if (!solve())
                ^
0_0_31307303_22627.cpp:262:16: error: in argument to unary !