foo.c: In function 'main':
foo.c:8:3: warning: ignoring return value of 'scanf', declared with attribute warn_unused_result [-Wunused-result]
   scanf("%d%d",&a[i],&b[i]); 
   ^~~~~~~~~~~~~~~~~~~~~~~~~
foo.c:18:19: warning: iteration 4 invokes undefined behavior [-Waggressive-loop-optimizations]
    if(a[m]+b[m]>=a[i]+b[i]) 
                  ~^~~
foo.c:16:3: note: within this loop
   for(i=3;i<=7;i++)
   ^~~

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