/in/foo.cc:9:1: error: expected initializer before 'int'
 int sum[20],
 ^~~
/in/foo.cc: In function 'int main()':
/in/foo.cc:16:57: error: 'c' was not declared in this scope
     for (int i = 0; i < m; i ++) cin >> a[i] >> b[i] >> c[i];
                                                         ^
/in/foo.cc:20:13: error: 'sum' was not declared in this scope
             sum[a[j]] += t[j];
             ^~~
/in/foo.cc:20:26: error: 't' was not declared in this scope
             sum[a[j]] += t[j];
                          ^
/in/foo.cc:26:13: error: 'sum' was not declared in this scope
             sum[j] += sum[j - 1];
             ^~~
/in/foo.cc:30:35: error: 'sum' was not declared in this scope
         for (j = 1; j <= n; j ++) sum[j] = 0;
                                   ^~~