View Compilation Error

0_0_15578742_20671.cpp: In function 'int main()':
0_0_15578742_20671.cpp:5:2: error: '_int64' was not declared in this scope
  _int64 s,a[51];
  ^
0_0_15578742_20671.cpp:6:2: error: 'a' was not declared in this scope
  a[1]=0,a[2]=1,a[3]=2;
  ^
0_0_15578742_20671.cpp:14:3: error: 's' was not declared in this scope
   s=a[b-c+1];
   ^