/in/foo.cc: In function 'int main()':
/in/foo.cc:11:9: warning: statement has no effect [-Wunused-value]
    for(a;a<=n-1;a++)
         ^
/in/foo.cc:16:8: warning: unused variable 'a' [-Wunused-variable]
    int a=1;
        ^
/in/foo.cc:35:8: warning: unused variable 'a' [-Wunused-variable]
    int a=1;
        ^