foo.cpp:8:6: warning: ISO C++ forbids declaration of 'main' with no type [-Wreturn-type]
 main()
      ^
foo.cpp: In function 'int main()':
foo.cpp:15:4: error: incompatible types in assignment of 'int' to 'int [50]'
 num=ch[i]-'0';
    ^
foo.cpp: In function 'void fun(int, int)':
foo.cpp:52:8: error: return-statement with a value, in function returning 'void' [-fpermissive]
 return 0;
        ^