View Compilation Error

0_0_35860588_813.cpp:11:4: error: 'M' was not declared in this scope
 }a[M];
    ^
0_0_35860588_813.cpp: In function 'int main()':
0_0_35860588_813.cpp:101:24: error: 'a' was not declared in this scope
    scanf("%d %d %lld",&a[i].x,&a[i].y,&a[i].z);
                        ^
0_0_35860588_813.cpp:107:12: error: 'a' was not declared in this scope
    if (dis[a[i].x]+a[i].z==dis[a[i].y]){
            ^