View Compilation Error

0_0_14756298_25604.c: In function 'main':
0_0_14756298_25604.c:12:5: error: 'sum' undeclared (first use in this function)
     sum*=num;
     ^
0_0_14756298_25604.c:12:5: note: each undeclared identifier is reported only once for each function it appears in