foo.c: In function 'main':
foo.c:8:13: warning: unused variable 'w2' [-Wunused-variable]
    int w1=1,w2=1;
             ^~
foo.c:9:4: warning: ignoring return value of 'scanf', declared with attribute warn_unused_result [-Wunused-result]
    scanf("%d%d%d%d",&x1,&n1,&x2,&n2);
    ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~

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