View Compilation Error

0_0_1817962_31059.cpp: In function `int main()':
0_0_1817962_31059.cpp:4: error: `sum' undeclared (first use this function)
0_0_1817962_31059.cpp:4: error: (Each undeclared identifier is reported only once for each function it appears in.)
0_0_1817962_31059.cpp:6: error: expected `;' before "while"
0_0_1817962_31059.cpp: At global scope:
0_0_1817962_31059.cpp:13: error: expected unqualified-id before "return"
0_0_1817962_31059.cpp:13: error: expected `,' or `;' before "return"