View Compilation Error

0_0_13232359_20313.cpp: In function 'int main()':
0_0_13232359_20313.cpp:8:1: error: '_int64' was not declared in this scope
 _int64 s,n;
 ^
0_0_13232359_20313.cpp:9:19: error: 'n' was not declared in this scope
 while(scanf("%d",&n)!=0)
                   ^
0_0_13232359_20313.cpp:16:4: error: 's' was not declared in this scope
    s=x+(a[i]-1)*x/2;
    ^