View Compilation Error

501933_0_0_23967.cpp: In function `int main()':
501933_0_0_23967.cpp:7: error: `_int64' undeclared (first use this function)
501933_0_0_23967.cpp:7: error: (Each undeclared identifier is reported only once for each function it appears in.)
501933_0_0_23967.cpp:7: error: expected `;' before "sum"
501933_0_0_23967.cpp:10: error: `sum' undeclared (first use this function)