View Compilation Error

0_0_31018528_15978.cpp: In function 'int main()':
0_0_31018528_15978.cpp:17:17: error: 'pos' was not declared in this scope
                 pos=i;
                 ^
0_0_31018528_15978.cpp:21:9: error: 'pos' was not declared in this scope
         pos-=2;
         ^