View Compilation Error

0_0_36161578_3994.cpp:24:11: error: '::main' must return 'int'
 void main()
           ^
0_0_36161578_3994.cpp: In function 'int main()':
0_0_36161578_3994.cpp:31:31: error: 'memset' was not declared in this scope
        memset(sg,-1,sizeof(sg));
                               ^