#include<stdio.h>
int M[4];
#define read(a) scanf("%d", &a)
#define write(a) printf("%d", a)
#define then
#define halt return 0
int main()
{
step1: read(M[1]);
step2: read(M[2]);
step3: M[3] = 0;
step4: M[2] = M[2] - 1;
step5: M[3] = M[3] + M[1];
step6: if (M[2] >= 0) then goto step4;
step7: M[3] = M[3] - M[1];
step8: write(M[3]);
step9: halt;
}
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