PKU 2017 Speed Limit [AC]

#include <stdio.h> int main(void) { int i; int set; int miles_sum; int mile, time; int prev_time; while(1) { scanf("%d", &set); if(set==-1) return 0; prev_time = 0; miles_sum = 0; for(i=0; i<set; i++) { scanf("%d %d", &mile, &time); miles_sum += mile * (time-prev_time); prev_time = time; } printf("%d miles\n", miles_sum); } return 0; }