View Compilation Error

0_0_21702307_13774.cpp: In function 'int main()':
0_0_21702307_13774.cpp:6:5: error: '_int64' was not declared in this scope
     _int64 a[51]={0,1,2,3};
     ^
0_0_21702307_13774.cpp:8:3: error: 'a' was not declared in this scope
   a[i]=a[i-1]+a[i-2];
   ^
0_0_21702307_13774.cpp:10:20: error: 'a' was not declared in this scope
   printf("%I64d\n",a[n]);
                    ^