View Compilation Error

0_0_13232222_5049.cpp: In function 'int main()':
0_0_13232222_5049.cpp:5:1: error: '_int' was not declared in this scope
 _int s;
 ^
0_0_13232222_5049.cpp:13:4: error: 's' was not declared in this scope
    s=x+(a[i]-1)*x/2;
    ^