View Compilation Error

0_0_1817809_4377.cpp: In function `int main()':
0_0_1817809_4377.cpp:5: error: `sum' undeclared (first use this function)
0_0_1817809_4377.cpp:5: error: (Each undeclared identifier is reported only once for each function it appears in.)
0_0_1817809_4377.cpp:7: error: expected `;' before "while"