View Compilation Error

0_0_24131492_14803.cpp:2:11: error: '::main' must return 'int'
 void main()
           ^
0_0_24131492_14803.cpp: In function 'int main()':
0_0_24131492_14803.cpp:9:46: error: invalid operands of types 'int [20]' and 'int [20]' to binary 'operator*'
         if(l[a]>1&&l[a]<=20&&n[a]>1&&n[a]<=l*l)
                                              ^