View Compilation Error

0_0_28136627_23179.cpp: In function 'int main()':
0_0_28136627_23179.cpp:4:5: error: '_int64' was not declared in this scope
     _int64 a,b,c;
     ^
0_0_28136627_23179.cpp:5:32: error: 'a' was not declared in this scope
     while(scanf("%I64X %I64X",&a,&b)!=EOF)
                                ^
0_0_28136627_23179.cpp:5:35: error: 'b' was not declared in this scope
     while(scanf("%I64X %I64X",&a,&b)!=EOF)
                                   ^
0_0_28136627_23179.cpp:7:9: error: 'c' was not declared in this scope
         c=a+b;
         ^