View Compilation Error

0_0_19854090_29622.cpp:2:1: error: '_int64' does not name a type
 _int64  sum[41] = {0,3,8};
 ^
0_0_19854090_29622.cpp: In function 'int main()':
0_0_19854090_29622.cpp:9:9: error: 'sum' was not declared in this scope
         sum[i] = 2 * (sum[i-1] + sum[i-2]);
         ^
0_0_19854090_29622.cpp:12:25: error: 'sum' was not declared in this scope
        printf("%I64u\n",sum[n]);    
                         ^