View Compilation Error

0_0_6879756_21960.cpp: In function `int main()':
0_0_6879756_21960.cpp:12: error: `longlong' undeclared (first use this function)
0_0_6879756_21960.cpp:12: error: (Each undeclared identifier is reported only once for each function it appears in.)
0_0_6879756_21960.cpp:12: error: expected `;' before "sum"
0_0_6879756_21960.cpp:16: error: `sum' undeclared (first use this function)