View Compilation Error

0_0_35911781_5888.cpp: In function 'int main()':
0_0_35911781_5888.cpp:19:8: error: conflicting declaration 'double n'
 double n=pow(y1-y2,2);
        ^
0_0_35911781_5888.cpp:6:8: note: previous declaration as 'int n'
    int n=4,first=1,i=0;
        ^