View Compilation Error

27731_0_16610.cpp: In function `int main()':
27731_0_16610.cpp:5: error: `_int64' undeclared (first use this function)
27731_0_16610.cpp:5: error: (Each undeclared identifier is reported only once for each function it appears in.)
27731_0_16610.cpp:5: error: expected `;' before "n"
27731_0_16610.cpp:6: error: `n' undeclared (first use this function)
27731_0_16610.cpp:7: error: `sum' undeclared (first use this function)