foo.c: In function 'main':
foo.c:9:5: warning: implicit declaration of function 'ys' [-Wimplicit-function-declaration]
9 | yu=ys(fm,fz);
| ^~
foo.c:5:2: warning: ignoring return value of 'scanf', declared with attribute warn_unused_result [-Wunused-result]
5 | scanf("%d%d",&b1,&a1);
| ^~~~~~~~~~~~~~~~~~~~~
foo.c:6:2: warning: ignoring return value of 'scanf', declared with attribute warn_unused_result [-Wunused-result]
6 | scanf("%d%d",&b2,&a2);
| ^~~~~~~~~~~~~~~~~~~~~
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