Multiplication Using Addition C

#include<stdio.h>
main()
{
 int a,b,i,multiplication=0;
 printf("Enter a,b\n");
 scanf("%d%d",&a,&b);
 if(b<0)
{
 a=a+b;
 b=a-b;
 a=a-b;

}
 if(a>=0)
{
 for(i=1;i<=a;i++) multiplication+=b;

}
 if(a<0)
{
 for(i=a;i<=-1;i++) multiplication-=b;

}
 printf("Multiplication=%d\n",multiplication);

}