View Compilation Error

0_0_26543142_31587.cpp:5:11: error: '::main' must return 'int'
 void main(){
           ^
0_0_26543142_31587.cpp: In function 'int main()':
0_0_26543142_31587.cpp:26:25: error: 'strlen' was not declared in this scope
             t1=strlen(ca);
                         ^