foo.cc: In function 'int main()':
foo.cc:37:23: warning: comparison between signed and unsigned integer expressions [-Wsign-compare]
     for (int i = 0; i < a.size(); i ++, time ++ ) res += a[i] * time;
                     ~~^~~~~~~~~~
foo.cc:38:23: warning: comparison between signed and unsigned integer expressions [-Wsign-compare]
     for (int i = 0; i < b.size(); i ++, time ++ ) res += b[i] * time;
                     ~~^~~~~~~~~~
foo.cc:39:21: warning: format '%d' expects argument of type 'int', but argument 2 has type 'll {aka long long int}' [-Wformat=]
     printf("%d", res);
                     ^
foo.cc:15:10: warning: ignoring return value of 'int scanf(const char*, ...)', declared with attribute warn_unused_result [-Wunused-result]
     scanf("%d", &n);
     ~~~~~^~~~~~~~~~
foo.cc:18:21: warning: ignoring return value of 'int scanf(const char*, ...)', declared with attribute warn_unused_result [-Wunused-result]
         int x; scanf("%d", &x);
                ~~~~~^~~~~~~~~~
foo.cc:21:17: warning: ignoring return value of 'int scanf(const char*, ...)', declared with attribute warn_unused_result [-Wunused-result]
     int m; scanf("%d", &m);
            ~~~~~^~~~~~~~~~
foo.cc:24:21: warning: ignoring return value of 'int scanf(const char*, ...)', declared with attribute warn_unused_result [-Wunused-result]
         int x; scanf("%d", &x);
                ~~~~~^~~~~~~~~~

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